Remember you now inherit this 900 rate until they leave and if they did leave after a year and you try the unit B way...bam...out of rent and reserves again.Unit D - 2nd year of a 5 year lease is good, but the previous 15 years is irrelevant because the owner sold it and the new owner can relocate or go bankrupt. 

For example, you'd have to lose Y% your tenants "and" you'd have to lose your job "and" you'd have to burn through $X in reserves "and" you'd have to not be able to sell at a Z% discount to current market value ... the more "and"'s you can throw at it, the safer you are, but if you throw too many "and"'s at it then you will never buy anything because you could always come up with a scenario that would bankrupt you ... so, the question is are you comfortable enough with all the "and"'s you've come up with such that you are reasonably safe (that is for you to decide), and if not, how do you add some more "and"'s.As for your specific situation, you keep saying things like "will be worth" ...

And if you mess up, it can bankrupt you. 

Brexit has exposed five bankrupt countries in Portgual, Ireland, Italty, Greece and Spain.

Banks can go bankrupt just like borrowers.

We found the company who owned the first property is now bankrupt (for about 3 years).  

Latest info out here is Oneal went bankrupt and a new firm purchased the waterfront property.

I want to get going but I'm not willing to bankrupt myself in the process.

Detroit goes bankrupt and your investment has diminished so much that you cannot understand how you were unfortunately to have picked one of the only bad areas of investing since just about every other place had done well.

In the past I think that the Builders will build until the Market collapses and then they go Bankrupt like Donald Trump and start over again when the Cycle starts up again.