I use the fact that other people charge extra as my no-cost way of making my properties far more competitive and desirable than that of other landlords. 

Classes are starting soon and I don't know if I should go to college if I desire to make real estate a full time job.

Go there and walk the streets and get a feel for the neighborhood.You are about to take $50k of your hard earned money and invest it in a piece of property, that should give you incentive enough to be the authority on that particular neighborhood. 

If divest, the investor will receive principal + their percentage of earned interest, less management and carry fees for the fund, as loans are paid back.

My desired niche is investing in duplex, triplex and fourplexs. 

Agreed that I have chosen two desirable neighborhoods.

For example: If you earn $10000 from your rental property and in your tax you show that you had $15000 expense (= $5000 loss), the next time you are applying for a mortgage for another property, $5000 will go toward your expenses (5000/12 for each month) and it will impact your debt/income ratio.Does anyone have an insight about this?

For instance, I have a tenant now who repeatedly pays after the first, and has no desire to pay before the 5th, which is the last day before the late fee kicks in.  

The added value will make your property more desirable. 

After completing several fix and flip projects in the Atlanta area, I am still searching for the ideal mission appropriate contractor to join my team who understands and appreciates how to work professionally with the investor/developer but with a desire to collaborate on the right design.