I’m finally moving forward with purchasing a small duplex with a fair amount of cash reserves and excessive credit card lines thanks to travel hacking (I don’t intend to use them, but it’s nice to have them there).

However, you are getting a fairly small return on your equity.

Whenever you are buying a property out of state you should do a few things to ensure it's as smooth as possible.

What’s a fair split?

I’m thinking I’ll look at the comps and compute a fair price based on those numbers instead of the current rent roll.

It would be worth the $100-200 for a half hour/hour of an attorney's time to ensure you are following the laws and create a plan going forward. 

I've done a fair amount of research into the benefits and drawbacks of different markets, but selecting one over the others feels like guesswork.

Should I hold the house for this buyer, given that the price she was asking for her own house looks quite reasonable, or should I put my house back on the market, assuming that the market in the neighborhood for that house is fairly brisk.

Why risk it for a fairly minor cost savings?

You guys will have to obtain an EIN from IRS website to file the partnership website, fairly easy process.