Line of credit, cash out refi?

No you do whats called a credit bid.. you already have your money in the deal and your expenses  and tax's if you paid those.. so what ever your owed plus late fee's and interest and foreclosure costs any money paid to senior lender and insurance any property tax etc.. all that is added into your credit bid that your entitled to.. your not entitled to more though. 

Here’s the catch: The brother would be stretching to make the rent that I’m currently getting on some of the other properties I own in the neighborhood and, apparently, his credit isn’t great.

Any property is going to need repairs at times so don't go into this deal cash poor or when problems arise you will stress out more than necessary.With your military schedule are you planning to self manage the other tenants?

If you have no money and he has it all, or you're an 872 credit score and he's a 514 it can still be done...but would you or he want to? 

I recommend looking into the local credit unions first (Charlotte Metro, Truliant, etc.).Also, in addition to the meetings @Karen Rittenhouse mentioned, I'd invite you to come out to the next networking meetup of local BiggerPocket members:Charlotte, NC REI Networking Meetup - Tues.

If the development is poorly ran the monthly condo fees rising and special assessments could get extremely expensive and you have little to no control as a minority owner in the building.Some investors try to control the board by buying up a majority of the units.If you use a broker or agent make sure they specialize in condo's if that is the way you want to go.

Lima One is great too especially if you have credit or debt to income issues to personally get a loan

Also HELOC's get more restrictive or lenders get rid of credit lines all together.

I know my profile is pretty sparse right now and I'm rather time poor at the moment, but I'll be adding to it as I get the chance.