Well here were a couple my question I had...1) how can I find out if there’s an existing mortgage?

plus if you don't charge interest IRS will hit U with imputed interest .. so you will pay tax on some of the income like it was interest income.IE you can do 3 and year and no more than 7 in your portfolio at anytime.. this is to allow mom and pop IRA investors to loan their own money I know this exists in Oregon..but if your in the business that's different. so if you have bought a park with 40 park owned and 10 rentals and you want to move those park owned to the tenants.. then yes your probably in the business.Eddie Speed has been working on a national committee to try to address seller carry back for US investors I don't know if he is making any head way. 

They all tend to "rehab" existing parks and hold them.I'm like you though.

If you are IN active Contract to Purchase an MLS listed property with an ASSIGNABLE purchase agreement, where you have put up EMD funds and have an active open escrow and you now advertise FOR SALE  the "assignable interest you have in a purchase agreement" (not the property) with language in the AD, Marketing Flyers or CL- Craig's List Ad's  such as; "We are selling / transferring our rights in an existing purchase agreement..." 

If your property has a panel that uses circuit breakers, the entire panel cover needs to be removed, this exposes a lot of live electric parts, and the tenant has to remove the existing circuit circuit breaker, disconnect a wire, and then reconnect the wire to a larger circuit breaker and then install that circuit breaker.

Cons:Needs good surface prep (flat smooth clean)Needs to be rolled with a 100lb roller at least ($20 rental at hd)Not waterproof over woodWill curl in hot/humid/direct sunlight sunrooms etc without being glued down.Applications we have done with success:Floor leveler over existing tile bathroom then peel/stick vinyl tileOver level wood floors (plywood) Over existing linoleum Over concreteOver damaged and stained oak hardwoods (when you pull it up it does not leave a residue)

From what you describe, assuming that existing rental income is honestly reported on your tax returns, you should be able to count both rental income from the existing property, and projected rental income from the other units in what you are buying, assuming a local REI-friendly lender with minimal/no overlays (those are the reason why you see conflicting stuff online). 

Both of which i don't think work because of the existing mortgage and estimated rent evaluation.

But I’m not going to open a business bank account for an LLC that doesn’t exist yet because I didn’t buy the property yet.

I would never pay down existing mortgages I would just let them play out.