I've been hesitant to raise the rent because I'm pretty sure I'll lose my tenant, and dealing with a vacancy and turnover from afar will be a real pain.I am pretty confident I can get $1800/mo.

If you want you can PM I can send you an article that shows a pretty good plan for this question 

You would evaluate your holding costs at the much cheaper FHA 203k interest rate or conventional loan interest rate, if you wanted you could inflate your return by assuming you would have paid $x in rent per month as well other than that it will be pretty similar.

Find yourself a lawyer who specializes in corporate law ... a thorough operating agreement is a pretty boiler plate document.

Sounds like you have a LOT of exciting things going on right now.This question gets asked pretty frequently, and the best advice that I've heard, and that I can give, is that you should definitely start NOW. 

I found a house that is pretty much a fixer upper and has good potential for to be a flip.

It pretty much only helps one room, but at least it is something if its more than a day or so for repairs/parts.

Firstly, I'm pretty new to the BiggerPockets community and excited to learn about real estate!

15% though is still some pretty big holdings to be developed.

Just trying to decide the best way to quantify a “good deal.”On a pure rental the metrics are pretty easy.