I know a 5/1 ARM is stable for 5 years, but is that over a 30 year period like a typical fixed?

the outbuilding is rotting, the porch on the house is a safety issue because of how old it is and the nails are all coming out.

To me that shows they are considering the safety of others and one better, are not so sick they can't even make a phone call.

I'm not going to get aggressive on deal flow (I'm a bit conservative of an investor) I'll use my cash as a safety net just in case and if I'm able to get a deal fully refinanced to complete BRRR the cash flow should be more than enough to weather a drop in rental rates if that were to happen.

You could serve a 24 hour notice for a safety inspection and check the smoke and CO detectors and take note of how it looks and whether it seems like someone else is living there.

Anyway, I used my own funds for the rehab, then took if to a portfolio lender and refinanced it at 75% LTV for 5.25% for 20 years (5 yr arm).

Since you won't have an arm's length transaction, and appraisal will likely come back conservative (read lower than you think). 

We have a mix of ownership at the moment: 2 of them are owned by the LLC, the rest are titled to a single partner.We also have a mix of financial instruments at play: 3 of them titled to a single partner have a mortgage with a bank, 1 of the homes owned by the LLC has a private loan, and the last 1 owned by the LLC is all-cash at the moment.I'm less interested in asset protection from the LLC since we're using Umbrella insurance as our safety net.My main concern is filing taxes properly and accurately (attributing gains and losses to each partner correctly), especially since we started down only-LLC ownership and transitioned part way to personal-and-LLC ownership of our properties.

Do they have a commercial arm?

The provider will make or break your investment, specifically the property management arm.