Most investors calculate cashflow after they have made an offer. Some do it after they have exchanged. By then the figures are not something you can act on. They are something you have to live with.

Run the model first, before you negotiate, not after you are committed.

This article walks through what the calculator models and how each input works. It is not financial, legal, or tax advice. The right assumptions for your situation depend on your personal circumstances and the guidance of a licensed professional.

The hold period matters, not just year one

A standard cashflow estimate stops at year one. Rent minus repayments gives you a weekly figure. That number is real, but it only tells part of the story.

The questions worth exploring before you commit are: how does the gap change over time, at what point does the property potentially transition from costing you to paying you, and what might the equity position look like further into the hold?

The calculator is built to help you explore those questions using your own inputs and assumptions.

What the calculator models

The property

Purchase price, state, and property type are the foundation. State matters because stamp duty is calculated automatically based on where the property is. Queensland, New South Wales, Victoria, and other states follow different thresholds and rates. As an illustration, a $720,000 property in Queensland attracts $25,425 in stamp duty under current rates. The same price in Victoria is calculated differently.

The rent

Weekly rent and vacancy weeks set the gross income the property is modelled to produce. Net rent after vacancy is what the calculator uses as the income figure in the model.

Management fee and letting fee are separate line items rather than a blended estimate. The difference between a 7% and a 9% management fee compounds across a multi-year hold. The calculator models them separately so you can see the effect.

The finance structure

LVR, interest rate, and loan term set the base structure. LMI calculates automatically when the new loan LVR exceeds 80%. That trigger is based solely on the new loan - not on any equity debt held against another property. Someone borrowing 80% on the new purchase has no LMI regardless of what equity they are drawing separately. Where LMI applies, you can treat it as an upfront cost or capitalise it into the loan. Both produce different equity deployed figures and different ongoing holding costs.

If you are using a guarantor, the model removes LMI. A guarantor provides additional security against the new loan, which means the effective LVR sits below the LMI threshold even if the new loan itself exceeds 80%.

Equity funding is modelled independently of the new loan. If you are drawing equity from an existing property to fund part or all of the deposit and costs, the amount accessed, whether you are using full or partial equity, and the interest rate on the equity draw are all inputs you set separately. The two loans sit alongside each other in the model. A buyer taking a 90% new loan with LMI and an equity draw from their existing property can model both at the same time.

Interest rate is modelled per year, not as a single flat assumption. If you have a view on how rates may move during the hold period, you can set different rates year by year and see how that changes the modelled cashflow trajectory.

Your offset balance

Every other input comes from the property or the market. The rent is set by what tenants pay. The rate is set by your bank. Your offset balance is the one input that comes from you.

It works across three areas.

Starting balance. To illustrate the mechanics: a $20,000 offset against a $576,000 loan at 6.5% reduces the interest calculated on that loan by approximately $1,300 per year, or around $25 per week. The actual saving in your situation will depend on your loan balance, rate, and offset balance.

These figures are for illustrative purposes only and are not a prediction or guarantee of any particular outcome.

Annual savings contributions. The offset input is not just a starting balance. You can also set how much you are adding to the offset each year. Setting $200 per week in additional savings, for example, would add approximately $10,400 to the offset over the course of year one.

The compounding effect. The interest reduction from the offset does not disappear. It reduces the net loan balance, which reduces interest in the following period, which increases the saving further. Annual contributions compound that effect.

Using the illustrative figures above: a $20,000 starting offset with $200 per week in ongoing savings could grow to approximately $30,400 by end of year one, $40,800 by end of year two, and $51,200 by end of year three, with the weekly interest saving rising from $25 to $51 across that period.

These figures are illustrative approximations based on the example inputs above. Your actual outcomes will depend on your specific loan balance, interest rate, offset balance, contribution rate, and any changes to those variables over time.

Two investors buying the same property with the same loan but different offset balances and contribution rates will see different modelled cashflow trajectories. The offset is the one input the investor controls directly.

The acquisition costs

Stamp duty is auto-calculated and pre-filled based on state and purchase price. Every other acquisition cost is a separate adjustable line: conveyancing, building inspection, buyers agent fee, title registration, and any other upfront costs. The total equity deployed figure updates as you adjust each one.

The hold assumptions

Capital growth rate, rent growth rate, and expense inflation are all inputs you set. The defaults in the calculator are examples only. The appropriate assumptions for your situation depend on your own research, your view of the market you are buying in, and the advice of a licensed professional. There is no assumption that is universally correct.

Running the model on different assumptions shows how sensitive the outcome is to each input. What does the modelled cashflow look like if growth comes in lower than expected? What does the equity position look like at year ten on a more conservative input? The model lets you explore those questions before you commit.

The shareable URL

Every input you change updates the URL in real time. Copy the link when you want to share the scenario - whoever opens it sees the same model with every assumption visible and adjustable.

What the model produces

The weekly cashflow gap in year one shows the modelled difference between rental income and total holding costs under your inputs. This is the amount the model suggests you would need to fund from other income or savings, based on the assumptions you have set.

The break-even projection shows the point at which modelled rental income exceeds total holding costs under the growth and rate assumptions you have entered. This is a model output, not a guaranteed outcome.

The equity access projection shows when the modelled property value, net of the outstanding loan, reaches a level at which equity may be accessible for further use. This also depends entirely on the assumptions entered.

All outputs should be read as illustrations of what the inputs produce, not as predictions. Before making any decision, seek independent advice from a financial adviser, mortgage broker, accountant, and solicitor as appropriate to your circumstances.

An illustrative deal

We published a breakdown of a $720,000 property modelled under the 2026 negative gearing changes, walking through how the inputs and outputs work in practice. You can read that here: Negative Gearing Reform 2026: What It Actually Means for Property Investors.

The figures in that article are illustrative and based on a set of assumptions that may not reflect your situation.

Access the calculator

The calculator is free to use. Click the link below, enter your email, and access it instantly.

Open The Calculator

Get the weekly property decision framework. One idea every week. No hype. No hotspots. Just structured thinking for investors who want clarity before they commit.

Sign Up Here

If you want to work through how this applies to your current position, book a discovery call here.

Book a Dicovery Call

Disclaimer: The information in this article is general in nature and does not take into account your personal objectives, financial situation, or needs. It is not financial, legal, or tax advice. The Nelis Group accepts no liability for actions taken based on this content. You should seek independent advice from a relevant licensed professional before making any decisions and always confirm the latest rules and thresholds with your state revenue office or relevant authority.