The home could use windows, hardwood refinishing, furnace in the future, and basement carpet are the major things.Before I would even try renting out the home I would want to pay a good chunk of my student loans off (if not all) and then pay off my sister - around $30,000.

We estimate about $35/sq ft for a cosmetic rehab, obviously if it needs major fixes like windows, roof, mechanical, etc. that would be an additional expense.

That is when you need to replace carpeting, paint walls, replace lights or plumbing fixtures, replace doors and repair windows, etc. 

Honestly I do not know why the previous owner spent so much on the furnace and Air conditioner when the house needed so many other things like windows!  

If you can see in windows etc...use local rules of thumb for $/sq ft for cosmetic rehab plus any major costs for HVAC, roof, foundation, landscaping/fencing etc...to determine rehab ballpark.

As Courtney mentioned, a problem at a 4plex can potentially affect multiple units (or all of the units), whereas a problem at one house will generally be contained to that one house....along those lines: if a problem occurs at a 4plex (like the electric going out, or a fire), it could affect all of your tenants, but a problem at a house only affects the tenants in that house...However, when you're doing things like tenant viewings, it is easier to only be driving to a single 4plex compared to driving around to four different houses (esp. if those houses are far apart).  ...also, the 4plex might only have one sewer main, one electrical main line, fewer windows/doors, and fewer things to break in general than four separate houses, which could result in lower operating costs...There are a lot of "double edged swords", too; for instance--it may be easier and cheaper to replace a roof on a single 4plex than on four separate houses.

All that needs to be done baring an inspection is a new bathroom a few windows and a water treatment.

Looking at your timeline, Id get pre approved now since it typically takes 20-30 days to close on a property once your offer is accepted which reduces your search window to 4 months or so.

This is the simplest method, but it also means your tenants are more likely to abuse the utilities by leaving windows open with the heat or A/C running, leaving lights on, ignoring the toilet that constantly flushes on its own, etc.3.

The house itself is in fairly good shape as the bank did many improvements including water heater, windows, furnance, etc.