Are there roof repairs in the budget, again with a special assessment planned.

If the house needs a roof (with tarps) and was priced below market, you wouldn’t come back after inspection and ask for a reduced price due to it needing a roof...At the end of the day you can ask for whatever you want.

Asking price $185k w $15k roof credit (in a way $170k but I like the credit at closing).

Look at the results of the general inspection but you could also do:-sewer-roof-foundation-electrical-plumbing

I have a decent job making roughly 65,000/year, I plan on sticking with rentals but my banker said the expenses are too high on one of my rentals to possibly get another mortgage, this is because I had to replace the roof on that unit.

Horizontal metal drain pipes are plugged and don't drain,leak at worst times.

The perfect flip for a newbie will typically need paint, carpet, counters, plumbing fixtures, and MAYBE some subcontracted roof, windows, electrical upgrade, furnace, etc.

What if a roof or major system goes out?

You can check existing storages using google map search "self storage near ...." and then visiting places to get an idea,  google earth looking at the roofs to estimate self storage use and estimate square feet, using tool such as radius plus and of course if want to pay for (which you should depending on how much money you are planning to put in the project) is get the feasibility study. 

Is the foundation cracked, falling in, water leaking, etc?