Most lending institutions will match other institution offers.  

Should I attempt to open a couple of more lines with other institutions so that I have more available credit to me or would that not work?

The reason that any real estate attorney won't do, is that institutions have in house teams of attorneys who spend lots of time making sure the institution is compliant with lending laws. 

If there isn't the board can institute one anytime and you could lose your right to rent.  

Also the Mises Institute has lots of other great/free resources as well!

There is an institutional investor looking to purchase my entire building, and if 75% of residents agree to the sale, everyone must sell.I would have substantial gains due to the outside of market purchase price. 

When traditional sources of financing are unavailable, many developers will look to private lending institutions to complete their project.

Richardson and Plano were really blossoming like crazy when I lived there for a year, however, it's probably getting pretty tough to compete with institutional money in the area now.

I plan on offering the current tenants the opportunity to stay by raising the rent by only $25, but also instituting a RUB system, making them pay for the utilities.

I would also try credit unions due to their flexibility (I personally like them; they may require some deposits at their institution, but could be worth it).