(since they'll both adjust every 5).What do I win?

When rates drop it's a WIN-WIN! 

So, if two offers are equally good, the owner occ will generally win.

If I can acquire it, she'll rent it for the mortgage price, and let me keep whatever profit I can squeeze out of the sale of her house, its a win-win for me because i'll have a no hassle tenant for the next few years, make so money from her sale, and until she decides to move, she's putting equity in my pocket.

Yes @Daniel Ahern, structuring is something you see a lot when people are trying to launder illegally gotten money or people that win big at the casino and don't want to have to pay taxes on their winnings.

If it’s relevant, I picked this thing up with cash that I borrowed off of a credit card (it was only supposed to be a month long loan, and I had 0% interest for a year, so I thought I was relatively safe).

really as simple as that.now there are credit card schemes some will charge you money for .. that get you to all at once grab a bunch of credit cards that have teaser rates of 0 interest with the idea that you can flip before the first payment comes due... but getting a bunch of credit then maxing out the cards will crater your score.. so be careful there and if you have an issue with what you used the funds for you now have a bunch of consumer debt at high interest that could bury you.. so be careful.. there are no Zero % loans and for most starting out its even hard to get a HML.. which will be 16 to 14 Apr with at least 20% down plus points and fees

Some credit card debt (will I need to pay off completely before getting mortgage?)

I'm also unsure if I should use a 203k loan to finance the rehab, I'd prefer to do the bulk of the work myself and bringing in trades when needed and then refinance to get cash out when we're ready to purchase the next MFH, so I could see there being more savings if I self finance the renos through one of my 0% apr credit cards or just pay cash. 

BUT if you are paying 22.9% on a credit card then it works the other way.