And we converted the garage into a studio unit.

If the driveway- garage differential is big (for example, the driveway slab is sunken and you need to raise the house, you'll end up with an even bigger gap after repair) you might need to replace the driveway. $$$$8.

My idea is to live in the garage and rent every room out for a total of 3200$-4000$ towards mortgage and my money going towards home repair. i am young and looking for advice!

Convert garage or carport.

There are 16 separate garages attached to the property that he is not utilizing. 4.

Aside from that, the obvious such as similar square footage, basement/slab foundation, condition, garage capacity, etc needs to be considered. 

I’m curious to know if a 3/2 home with a detached 2-car garage and a separate “mother in law” 1/1 unit will be considered a duplex?

But Have to be aware and compare that most of the time (depending on area and on this market) Retail buyers or the "market" is paying a bit more for as is outdated houses ( so you check for those)  and also Check updated houses cos the ARV(After Repair Value) will increase what the market will usually pay for a better condition and modern house. 

I'm not sure about rates for owner occupied, but I use American Modern insurance on my 4plex.

If you have a detached garage you can still turn that into an ADU and have three units to rent out.1.