I just tell them, they can apply but it is probably not worth their time and money because I wont be able to hold the property vacant for that long.

I feel that if I build new I wont have a issue for 10 yrs and I wont need to compete with other investors.  1.

their are lenders though that we wont accept offers if our buyers are using them and Rocket is one of them.

Many management companies archive or destroy old applications because they do not want to be responsible for SSNs getting out to identity thieves. 

Are there any challenges or reasons why some of these tenants wont be able to pay through the software that I am not aware of?

Since you aren't looking until next year, you wont' be able to get a rate quote now, most likely not until you are under contract and they can lock that in. 

There are much simpler solutions that wont cost you 18K. 

All this as well as keeping an eye out for off market properties and sending them over to the client even though we really wont get paid until they decide to sell it if you are still their realtor by then lol. 

They're out there, you just wont see as many focused in the investment space as you will in the residential space. 

They wont have it either and they won't have their CDC guidelines or excuses.