Rents typically follow the "Common rents" of the neighborhood which your agent should know or have access to in most cases.

The STR doesn't provide access to rest of house as common area so they have their privacy mostly.I'm sure you can creative with extra rooms, a garage turned living space, ADU, a furnished basement, etc.Good luck!

You qualify for 100% financing and the closing costs can be covered by getting "Seller credits" which is fairly common in this market.

One being that you are only able to utilize the entity itself to roll the entirety of the proceeds into a new asset... which is not the ideal scenario. 

Sub 2 is a great tool, but having a couple of different tools in your tool belt will help you navigate different scenarios!

Another scenario would be to get an empty lot, build a multi-family and live in a unit.

Make sure you present the scenario to a mortgage broker or a local bank 

A C-10 Electrical contractor can explain how to split the units, you may have to sub meter yourself.splitting a single unit in 2 is generally more complicated than building a common wall. 

It is a common mistake.

Really look to see what scenarios could derail the investment.