The main concern here would be the liquidity that you have for this scenario.

As an "employee" with a solo 401k you can contribute up to 100% of your S/E earnings up to $23k/$30,500 over 50). 

At the end of the day, you are pledging an asset (stocks, in your example) for potential liquidity.

Miciah,Phoenix market has changed drastically since 2020 and has made the cash flow market very tight if you're not walking around heavy in liquid.

We have approximately $150k liquid cash ready to go and can likely gain more capital in a fairly quick manner. 

So if you used the $100k from your refi to buy an investment property, then 20% of the new mortgage interest becomes deductible on Schedule E against the investment property.Interest tracing is basically a concept used to prove that the $100k was indeed used as a down payment on that property and not for your new Ferrari.

You've been able to save up and have $50K in liquid cash.

Which allows you get up to 80% liquid.

We do not use a savings account for e. lease.

You've been able to save up and have $50K in liquid cash.