Yes, as S-Corp owners receiving W-2 wages, employee deferrals to a Solo 401(k) are subject to FICA taxes (Social Security & Medicare).

If you're willing and able, I do recommend the "house hacking" strategy which is just a fancy name for buying a rental property and living in one of the units, because you'll get very favorable financing - an owner-occupied fixed-rate 30-year mortgage.I'd also say, analyze that property as if you won't live there and it's a pure rental, and make sure the property is still cash flow positive if there's a tenant in your unit because then you'll know if it's actually a good investment.And when you analyze it, include payment of a property manager in your #s because if you don't, and doing so would make it go cash flow negative, then you've just bought yourself a job because you literally can't step away from managing it without losing money.

Preforeclosure owner finance wrap, paid off the default payments and taxes with cash and assumed the owners loan.

I would do you due diligence but I have seen others use it to purchase non -owner occupied properties.

I have a property that I could sell for somewhere around 400 K with owner financing.

For example, my appliance store gives me a 10% discount, so I charge a 5% markup to my owners to make a little money and the owner still saves 5% from retail. 

Preforeclosure owner finance wrap, paid off the default payments and taxes with cash and assumed the owners loan.

In addition, the gas bills have shut off notices and are not being paid. (3 units are occupied and utilities are all paid by owner).

Most of the rebates go directly to the MHP owner.

You'll have access to owner occupied loan products, therefore saving on your down payment, typically 3-5% compared to 20-25% for non owner occupied properties.