Don't overcapitalise. Got inlaws who are great at overcapitalisation, they have the nicest little house and before that the nicest little unit but their mortgage is always at the absolute maximum it can possibly be.If we did all that we prob wouldn't want to move!
There's a big difference between what you can do to a top-end house for sale and what you can do to get the maximum rental amount.
Maxing your rent is usually as simple as making sure the kitchen is vaguely modern and nothing is broken, house has aircon/heating and decent window dressings, floor coverings are clean and newish and don't look threadbare, and the paint is all good and not a hideous colour. Basically just bring an older house up to the same standard you'd expect in a project home built in the last 5 years. No need for pure wool carpets, european appliances, genuine marble benchtops etc, those don't add to the rent unless you're right at the top end.