Using their in house lenders can help substantially with loan terms. 

I have a gutted carriage house on the back of my property, so my thought is to get my feet wet with house hacking by creating space for a longterm tenant. 

It's best to get licensed so you will have a competent broker, a second set of eyes on the transaction who will help keep you out of trouble. 

Consequently, the house could not be made ready for the new tenants and after a big scramble, we managed to save the new tenants but lost 3 weeks of rent. 

We did get negotiate money from them to help with roof repair, but now know they were not honest on their disclosure.Our inspector missed code violations, HVAC issues, pipes that had been worked on and issues hidden that had occurred while sellers lived in the house, signs of drainage and water damage inside the house that had been painted over, completely blocked dryer vent...and we are finding more daily.We have had the house looked at by a structural engineer and HVAC techs that has told us we need thousands (likely tens of thousands) of dollars worth of repairs to make this property able to rent and come up to code for rental. 

I set up the solo 401k and I am the admin and trustee.

Checklist: Here’s a quick checklist to get you started:Get a home inspection (optional but recommended)Fix any outstanding repairs or issuesCreate or customize your lease agreement (covering pool/fireplace)Set up tenant screening processesTake detailed photos of the propertySecure proper insurance (consider rental-specific policies)Establish a move-in/move-out inspection processClarify utility responsibilities in the leaseConsider a property manager if you prefer hands-off managementDon’t worry, you're on the right track by doing your due diligence.

I am finally looking to put my 203k house hack team together.

My advice is to house hack the property that you end up purchasing.

Sell the house as is or use the lot to build new construction and sell for 2.5+.