And always have an extremely thorough contract that outlines exactly what is expected to be done, who is going to pay for certain materials, and when payments are to be made.

@Jacke DraperWhile you cannot create any kind of transaction where your Solo 401(k) and personal funds intermingle as you have outlined, there may be a way to get your deal done.The Solo 401(k) could purchase the property and obtain a hard money loan for the rehab costs. 

In Texas required to present you with a disclosure called "Information about Brokerage Services" outlining the various relationships Agents can form with a prospective Buyer.  

I can tell you, from 10 years experience, it isn't nearly as SCARY as you've outlined it here.

I have this outlined on the first page of the lease so the tenant knows exactly what items need to be done before they get the keys and can move in.  

The completed loan file will include things like: Bank statements to prove liquidity, maybe an ACH form for the auto payments, an insurance binder to prove the house will be insured, a rehab budget template that outlines the complete scope of work, an experience spreadsheet that list all your completed projects (this is blank if this is #1), your entity docs, your ID. 

Exactly as your agent outlined, nothing fishy about that at all.

The LLC outlInes how the assets are treated and divided.

There are some additional charges (eg. changing the locks on your properties, calling you for repairs over a value that you set, etc), but no charges that are not clearly outlined in your contract.

I would start with an outline of exactly what you are looking for (what services are most important) and how much you are willing to pay.