To add on a thought to your post, one which you've already implied. 

As a resident and residential investor of DFW for the past 23 years I agree with everything said here and it's all good advice.I'd like to add one "key factor and risk" you asked about.

Still,  should I add-on this future income for pre-qualification?

As others have said, you're unlikely to get immediate, passive cashflow in any of those markets (certainly not Austin, where I work and invest) unless you plan on either 1. putting a lot of money down, or 2. doing some type of value add. On

I'll just add on to make sure the land you buy doesn't have any fatal flaws before you close on it, i.e. make sure there are no weird things on title, i.e. easements, encroachments, and that all the utilities that you need are there, and it has legal access, etc.

But for 3 bedroom apartment, you try to add one small Half bathroom and cut out the living room, you can get $2500+ by renting to student. 

Also, keep in mind that PMs often have add-on fees for tenant placement, managing repairs etc in addition to collecting a fee for monthly management.

Can you add on?

Is that 60 single family and you want to go to 200 single family, or do you want to add one 140 door apartment building?

There were then two add-ons, one for the calculator the program uses that you didn’t have to buy, and another to make all the 5 days worth of classes available for 30 days after the program was over.