Property tax and insurance escrowed into mortgage, paid from regular income.
If I understand right, you'd be living in the main house and rent the extra apt? In that case, I think you're mainly looking at having other people in your space. The money is obviously beneficial and not so much profit but mortgage reduction (as I assume the alternative is buying the house and leaving the apt empty or buying a different similar priced house).
In return for the mortgage reduction, you'd have other people around. You should think about this. How many people? Will they have loud parties? Hang out in your yard? It's different renting part of your home (I previously rented my extra bedroom, at least you have separation!) than a dedicated rental unit across town.
How much of your mortgage would the apt rent offset? I would think of it like rather than the typical rental cash flow model since its part of your house. In my case it was 60% of all household expenses (my SO and I split the other 40%, so paid very little each) being paid by my renter so it was worth it even though they were at times annoying but eventually, I'd had enough still and needed then space.
Basically, the hassle would be having someone else around who while paying you, might also drive you nuts. So choose wisely 😀 And consider doing a month to month arrangement.
