I have heard $500K thrown around as a general rule of thumb (will vary by firm).

If you want to start as an agent, you will probably make little or even lose money your first year, so you will need some money put away or a spouse to support you. 

You don't have to have all cash, your IRA can buy a property using leverage but you must utilize non-recourse financing (no personal guarantee is allowed according to the IRS rules).

As you are from Sacramento, do you know Los Angeles rules at all?

Perhaps you have a plan provider with meaningful support.

I would keep the expenses split 75/25% subject to the rules of the solo 401k.

If posting this is a violation of the rules please feel free to remove it.

Part of our california broker rules is that we are not allowed to discuss pricing, but I can give my recommendation to have a very detailed mgmt agreement in place with your owners  who takes care of Insurance payments, claims, repairs, tenant issues, HOA violations,  When do you pay the owners> Do you keep a reserve from them to pay for repairs?

Just be firm with rules, posting notice when they're late, etc...

I support what everyone said above.