This leaves me and my partner to split the other 2700 portion to close.

Closing on the property happens, then shortly thereafter he/she has life changes, or whatever, and wants to leave their W-2 job and go to self employed or something other than full time W-2.

Now we have tenants that try to leave their old flat screens behind.

He has no right to have it there or leave it behind.Call the police about the two vehicles and report them abandoned.

Its easy to say take it or leave it but you need to be sure you are actually okay if they decide to walk. 

And no - there isn't a refund once they leave, you just decided to prepay your taxes while you move on to the next "buyer". 

What if they break-up and the primary tenant decides to leave, does it mean that the sub-tenant must vacate as well?

I wouldn't ask the tenant to leave.

@John Williams - One way I have done it is by finding home owners who were willing to sell me their home and leave the existing mortgage in place (also known as Subject To Financing). 

Also considering a big private loan, but as there's no telling how long before some of these will be vacant (they're all MTM but don't want to jack up rents so high that everyone leaves) so I don't want to be in private money for an indefinite period of time...