The model: Two parallel simulations run from year 0. The base scenario grows your existing portfolio at the market assumptions (capital growth, rent growth, interest). The enhanced scenario does the same but at the year you specify, applies each value-add play — pays the cost from cash, lifts the rent by the uplift, adds the value uplift to your equity. From that point forward, the enhanced portfolio earns more rent each year, which compounds with rent growth.
The preset defaults are realistic Australian numbers, not spruiker numbers:
- Granny flat: $180k build (incl. site costs + services), $450/wk extra rent, $130k value uplift. Eligibility and approval requirements vary by state and council — some allow as exempt/complying development on larger lots, others require full DA. Check your local rules.
- Dual occ / duplex: $300k cost, $700/wk extra rent, $300k value uplift. Two dwellings on one title. Significant DA + planning required.
- Rooming house: $80k conversion, $600/wk additional rent (above standard), $50k value uplift, $6k/yr extra costs. 5-8 rooms. Council registration, fire safety, and maximum occupancy rules vary widely — some councils restrict heavily, others are more permissive. Higher management hassle.
- Subdivision: $80k survey + costs, $0 rent change, $400k value uplift (sell off the back block — releases equity to redeploy).
- Cosmetic renovation: $40k spend, $80/wk extra rent, $60k value uplift.
- Short-term rental (Airbnb): $25k setup + furniture, $400/wk uplift over long-term rent, $8k/yr extra costs (cleaning, fees, restocking). Much higher work.
What this calculator deliberately doesn't model:
- Council approval risk (some plays may not get DA at all in some areas — assumes approval succeeds)
- Construction delays or cost blowouts (assumes you complete on time and budget)
- Borrowing capacity to fund the plays (assumes you have cash or accessible equity)
- CGT impact of subdivision (selling part of a property has complex CGT — see your accountant)
- Higher vacancy for rooming houses and STRs (built into the management cost estimate)
- Depreciation (value-add builds generate substantial depreciation that this doesn't model)
- Land tax aggregation (multiple properties in one state can push you into much higher land tax brackets)
Use this for: Stress-testing whether value-adds are worth your time and capital. The honest framing is "given a fixed starting position, how many years can value-add plays save?" Different plays suit different properties — granny flats need lot size, rooming houses need zoning, STRs need location.