Then an inventory of the size of units for the 83.  10/15/20/etc. 

I moved into a somewhat decent sized apartment complex for six months between houses. 

New homes are going to have virtually no repair, maintenance, or capex needs for the first five or so years, so you’ll be able to forecast your operating expenses and cash flow with a bit more certainty from the outset.Older properties, however, are generally more affordable than a new home of comparable size and build quality, so if you’re after a good deal, you’ll likely have more luck here—especially if you’re willing to look beyond the MLS for deals.

You can have two properties with similarly sized roofs in two completely different neighborhoods at different cost points. 10% "might" be a starting point, but it depends on a lot.

For example, if you are looking to get $1,000 a month and all the available rentals on Zillow have hardwoods for a comparable-sized property/ unit you would want to add hardwoods.

Sure, you can make your unit extra special through design or amenities but when most of your competition is similar in size/shape, those extra items can only warrant so much of an increase in ADR. 

Usually you need to have some experience before getting funding, however it will vary largely on the size of the rehab.

For my first property I'm going to use the BRRRR method and from there keep growing my portfolio.I used BRRRR to grow a "medium" sized portfolio in and around Atlanta that I am very happy with. 

I do not think this is a one size fits all answer and there are times where private lending is preferred over traditional financing.

I'd also look at other things like the size of the home (and rooms), layout and size of the lot.