Treat them as a lender with fixed return or equity with share of profits if they're all passive (ie you do the work).Make sure you account/bill for your time.

If they are going to be a passive investor while you do all the work, this may be treated as a security under the rules and regulations of the SEC.

If you do not follow proper formalities, a court can rule it is not a real business and treat you as if you don't have an LLC (called Piercing the corporate Veil) I recommend the self help legal books by NOLO Press.

Mobile home park owners treat everyone the same whether they own 1 or 100 properties -- that's what makes it interesting.

How can I legally force A to have an exterminator treat his unit?

The issue is the type of financing you can obtain. 1-4 units is treated the same, and being an owner-occupant can help you get favorable terms from the bank such as better interest rates or a lower down payment.

For the hold, I recommend treating it as a flip...

Banks do loan to unmarried couples, but, from what I've seen, they tend to treat them as two individuals rather than one unit.

I won't discuss CCorps as I spend very little time on that arena.I will fully agree with talk to an attorney to help to draft up the paperwork properly depending on what situation you are in and what you are trying to accomplish - a different transaction structure such as a straight asset sale could be a better choice.1) If the entity is formerly a partnership, now disregarded, rev rul 99-6 walks through the analysis that has us treat as an asset sale 2) If the entity is formerly a partnership, still a partnership, 754 gives you an avenue to agree inside and outside basis3) If the LLC was disregarded, and still disregarded, we also treat as an asset sale - the assets are treated for federal tax purposes as held directly by either party.4) entity was disregarded and now a partnership - rev ruling 99-5 provides the mechanism for what is effectively a step up.5) if it was formerly an SCorp, we can maintain SCorp status and run a 338(H)(10) transaction to achieve a step up in basis in the underlying assets.

And I think that knowing U.S. law, including as imparted through Nolo Press, will help you to be fair, & even-handed in dealing with tenants, which is important, due to many people will treat you back, the way you treat them.