Once a house my brother and I co-own (inherited property in rough condition aka not getting rich off it) sells in Vermont, I will be debt-free and have some savings for a down payment.

I would (and did) save up $1 or $2k.

I self-manage and because of the aggressive 15 year mortgage I take home just $450/mo which just goes into a savings account, so I don't split out repairs and vacancy. 

Probably saved me $20k in missed flip items.

If you set up an LLC, you might be able to save in some areas, but pay in others (for example, here in California, we get to pay $800 a year just for the LLC registration, regardless if any profit was made).

Wait a second...I re-read your post, you save $25K every 3 months?   

(If you are in the Denver market that should feel like a different planet) There is nothing remotely close to listed in denver (even in adams county) for less then a gross rent multiplier of less than 130 times monthly rent.

I have an idea but I'm not sure it'll work legally or if I'm missing some information.I work for the government and currently contribute 5% (tax deferred) into my Thrift Savings Plan (TSP) since my agency matches up to 5% (100% of first 3% then 50% of other 2%).

Most of the scenarios proposed to us by potential clients for such joint ventures would likely create a benefit between the parties and not pass scrutiny in an audit.There are many ways to safely and productively grow your IRA investing in non-traditional assets such as real estate in a standalone fashion,  There is no need to take unnecessary and foolish risks with your retirement savings.

Should I bite the bullet and pay down the house and get 100% cash flow in about 5 years with early payments or should I refiance to a 30 get instant cash flow and save up for a second home?