It’s currently rented for $2,200/month, with a mortgage and HOA fees totaling $1,900/month.

Regarding turnover: This depends on whether you have them sign a 1-yr. lease, Semester lease, 10-month lease, etc.

In the above two apartments the tenants were consistently behind on rent and when they left were probably each about three months behind.3. 

They pay me good monthly cash flow and are paying off my mortgages, and I do them a solid once in a while and let them improve my homes the way they want.

Between paint and flooring that are sometimes needed, and months of vacancy, it would take me YEARS to recoup those losses even with new rent increases.

It will be done correctly every month and during tax time, you and your partners can easily have to CPA/book keeper issue 1099's and get your taxes filed on time with all the right deductions.

am I legally allowed to keep her last months rent and security deposit?

I have properties that would rent traditionally for $700-1000 a month, it's not unusual to pull in 3-4X that in a typical month, even 2x that in low/offseason.

I recently acquired two properties in North Carolina for rehab and flipping in next 2-4 months.

Inspections take for absolutely ever so I know many would be permit pullers are skipping the process because it can take a month to get an inspection.