(You still must of course keep the unit habitable,  and that could still be quite costly depending on the shape of the building)And when it does come to raising rent,    if possible do it in a few steps so it gives them more time to adjust.   

These must comply with HUD or state laws depending on where they are manufactured.

Depending on your credit score and a few other factors, you won't need a ton of cash if it's your primary.

But, depending on loan to value and credit should be able to do much better then 10.24%.And the 10 number you mention is only for conventional loans.

Another benefit depending on the seller's tax situation is that they can spread their cap gains and depreciation recapture tax hits out over several years rather than paying it on the lump sum in a typical sale. 

Depends on whatever the partners agree to.

I don't believe there is a common practice, its going to be dependent on local standards.

Given that it's an ADU and you are an owner occupant I would courteously terminate the lease (the how on this is going to depend on your local laws and your lease) and get a new tenant ASAP.

I believe in many circumstances a permit or use license will be required by the municipality depending on the use. 

As I tell all individuals wanting to invest out of state, regardless of the market, your success rate will largely depend on the resourcefulness and reliability of your team (agent, lender, property manager, contractor).