Common sense.

Typically, at today's prices, to keep a house in good condition long term, you probably need to reserve about $400-500 per month for things like roof, HVAC, water heaters, new flooring every 10-15 years, new kitchens and baths every 10-15 yrs, etc.And remember, if you are looking at "high cash flow" areas (also known as lower end areas) with lower end rents, a refrigerator that goes out does not care whether you are getting $500/mo in rent or $5,000/mo, so using a percentage of rent, as commonly practiced, is not a good strategy.  

What is more common is that our clients will have a back up purchase like a Delaware Statutory Trust identified to buy into if one of their purchases fails. 

@Dominique Coffin,This is much more common in our current interest rate environment. 

What all are common items included in closing costs on a wholesale transaction?

It isn't very common but it could be done.

That's called common sense where I come from.

Quote from @Candi Kham: SOFTWAREGood software will handle management, accounting, and application screening.Software is a common question on BiggerPockets.

DTI is a common challenge that we all face, however, it sounds like you need a lender that is going to help you look at the overall situation and give advice as to the best course of action.

Permanent rate buydowns usually have 5-7 year break-even points, though lately 3-5 is more common with some lenders, but that still means an 87.2% chance of NOT breaking even, since 3 years is longer than 2 years.