Landscaping has the largest ROI (of about 200%), adding a wood deck or a patio will also provide a big increase in value (100% ROI).Add living space, consider converting attic space, finishing a basement, or repurposing a large living area to add a bedroom without expanding the home's footprint - this will give you an average ROI of around 75%.

First I would go to the Building Dept and see if the existing garage is allowed to be converted.

2 Years ago today, instead of renting a studio apartment, I bought this 3/2 single famliy house in Apopka, Florida, rented out the 3 rooms and converted the office into my bedroom.

Your financing: not sure what that would look like, but your operating expenses and PITI could determine whether this place could be converted to LTR, MTR or might only work as rent-by-room or STR. 

The seller’s equity was essentially converted into a loan to you, which you're paying back with interest.

We ended up opting for a heloc but two months later converted the duplex to an str. 

The STR's here are primarily second homes that out of staters have converted over after realizing the returns they could get.

Some alternatives that I have considered is purchasing a single-family home, living in it for a year as a primary and then moving and renting it out, or looking for a single-family home with a decent-sized basement and converting that into a unit.

I was looking to have it convert to a long-term mortgage and eventually cash out refinance to build a second duplex once enough equity built up 

You can plan to convert to a LTR as a backup or if you’re starting out only buy where you’d ultimately want and could afford to maintain as your personal vacation home if needed.