Right now it is hard to predict rent increases since there are a number of factors that go into what rent rates are including supply and demand of housing, interest rates for mortgages (low interest rates turn renters into buyers), inflation, and prices of homes sold.I know the BP calc has a box for implementing rent increase but I usually leave that as 0% and only plan on what current market rents are and count on any increase being the icing on the cake.Tax rates are also more complicated than just a % of the sales price but a great lender can help you estimate the exact tax amount of a property you are going to be buying.

You could potentially do a reverse exchange (where you find and buy the replacement property first), which is not too much more complicated than a traditional 1031, and a good QI can hold your hand through the process. 

I have a doubt about a wholesaler,by the way I would like to become one, what are their main challenges?

Some people do that, as a matter of fact.Your scenario has a complication: you're moving into a rental you already own.

Without facts, I am just speculating and speculation complicates investment decisions. 

(This suggestion of a "debt" position or note investment with the SEP IRA to avoid UBIT and UDFI tax is a creative one... but it’s a very low chance of happening because it’s just too complicated and honestly not worth the effort from the syndicators side.

It can be as fast as 2 weeks and take much longer if it has some sort of complications like access for fire personnel and that sort of thing. 

A bit paranoid I know, but life/real estate is already complicated enough, and this is basically a long-term relationship and physical alteration affecting the property.

The math is not that complicated once you get used to running the numbers especially on smaller residential properties.

It complicates your life for no reason.