With him being in a all cash business, it creates a unique situation where he will be getting is money into the deal by raising the value of the property and paying for everything but the down payments.

I will be doing a few updates to that side of the duplex and raise the rent up to the market value for the area.

@Carl Mayer Unfortunately, northern Colorado is not immune from the issues facing the entire front range and that is an influx of people and not enough places for them to buy.

I'd write each tenant a letter upon closing stating that you do intend to raise the rent, but slowly.

I intend to keep acquiring [cash flow positive] rental properties through BRRR and hold them long term.I have quite a bit of friends and family who also wants to 'invest in real estate', but don't have the time or are in geomarkets that aren't ideal for the BRRR strategy.Have any of you partnered with multiple investors to raise a fund that is specifically used for acquiring longterm rentals?

It does not provide a whole lot of cash return in the short term.But if your goal is to buy off-market properties for below market value, rehab them, raise rents, increase the property value, and flip them after a year or so, then you would do better to find money partners now so you can start getting those deals and churning that money.  

Thinking of investing in Saint Louis where I was born and raised and know the area.

It will not hurt your credit score significantly (1-5 points max for a hard inquiry) but it may raise a red flag to the lender doing the refi.

And if it shows up my immune system will eat it for dessert. 

@John Neff If you are interested in developing partnerships, perfecting communication skills or raising capital as I am, three books are top of mind and I don't think have been mentioned:Raising Capital for Real Estate by Hunter ThompsonFlip The Script and Pitch Anything by Oren KlaffOf course, as mentioned already "Never Split the Difference" by Chris Voss is a phenomenal book and The Book on Rental Property Investing by Brandon Turner is great for a new investor.Finally to take back your day as all this Real Estate Investing begins to occupy all your time: "Own the Day" by Marcus Aubrey is a great read.