Maybe you are referring to actually having to have a cash outflow when it was not desired.Maybe draft the partnership interest in such a way to mitigate this kind of situations. 

It's kind of cool as I get to see accounting in real life.In regards to your questions l, the IRS issued new regulations about capitalization of assets, and capitalization falls into four categories, Betterment, Improvement, Adaptation or Restoration.

Or can I just meet up with all the parties and create some kind of contract?

I once read that you should only invest your money after having a "cushion" saved up for these kinds of emergencies. 

Best kind of loan / mortgage I should get?

That solved all kinds of problems for all kinds of people.

She informed us that she already paid the other owner June’s rent, which I kind of figured it would happen.

Do you guys keep security deposit in a separate bank account and if so what kind?

Maybe mobile homes need a different kind of loan; I'm not familiar with those. 

So stay engaged and ask all kinds of questions as well as take a look at the blogs and the pod cast.