This allows you to control renovations and decide whether to self-manage on the back end.

I hope you are asking two separate unrelated questions, because there's no point in doing cost segregation for properties held inside your self-directed solo 401k, save for some very rare exceptions.Some of the Bigger Pockets experts who operate reputable costs segregation companies are @Bernard Reisz, @Yonah Weiss and @Julio GonzalezSome of the Bigger Pockets experts who offer Solo 401k administrator services are @Dmitriy Fomichenko, again @Bernard Reisz and @Brian EastmanReach out to them and see if they can help.

If you go too low I would either recommend self managing or liquidate it. 

For those managing active income streams—like wholesaling, flipping, or even running a real estate business—filing as an S-Corp can significantly reduce self-employment taxes.

Plan was to do self storage; then found out the creek that sits a ways back flooded 5 years ago, not in a floodzone but all the locals know so self storage is a tough sell at this point. 

You only get paid enough to continue.3) You don't need a dozen self-help books, all you need is action and self-discipline.4) YouTube University, podcasts, and the internet will only take you so far. 5) Book smarts make interesting conversation, street smarts make money.6) Find someone who is successful doing what you want to be doing and ask questions.

Or keep building and retire your self sooner.  

Here are the numbers:Purchase price: 300k @5.5% (might be able to negotiate new exterior paint job credit)Monthly costs: mortgage- 1703 tax-245 (2933/yr) insurance- 167Market rents are 1600$ easy for both sides as is but currently being rented at 1410 and 1325 tenets pay all utilities (separately metered)Planning on putting aside 20% of rents for Maint, vacancy, capex and will be self managing property.

You just need to have certain minimum underlying requirements per policy exposure.I do agree that having $1 million in underlying coverage is not a sufficient reason to not consider an umbrella policy. 

Like others in the post, interest income is portfolio income.What you can do is invest a self directed IRA/roth and put this money into notes.