I desperately need my own place for myself and girlfriend and her 5 yr old son. 

I would never sell sub2 unless I was really, really desperate.

Do I then have to try desperately to get one of the other 2 properties under contract and closed by the end of the 180 days?

The landowner will have a great negotiating position when you have built and maintained a rental property and are desperate to renew your lease or purchase.

It's old and desperate.

@Steve Cribb to be successful, landlords need to set boundaries.Many tenants, especially desperate ones, try to make their problems their landlord's problems.As a PMC, we try to be reasonable, as "life happens" and "tenants are tenants for a reason", meaning they don't plan well and live paycheck to paycheck.Part of our being reasonable though, involves deadlines and we AUTOMATICALLY start the eviction process so a tenant knows this. 

And in this case, it's because the government is bankrupt and desperate to attract investment.

However at some point I was desperate to live by myself - to get to experience that freedom so for about two years I paid two rents, two sets of utility bills (this was before I knew anything about REI) then decided she can move in with me again not only to save some money but because she was getting depressed on her own.

Some tell me how desperate the sellers are.

. - If the seller is desperate to close (due to health issues, family problems, liens, etc.), they may agree to Seller Finance the small amount in order to ensure the deal makes it to the closing table. - You're minimizing how much is coming out of pocket when closing arrives.