It's almost like they tack on a few hundred dollars to the order and forget to charge sales tax

Can provide all the benefits from a cash flow and tax perspective.

Worse case I just continue to manufacture them through my fix-n-flip business and buy with seller financing where available.Also, is tax lien investing really viable today? 

I guess it can save you some time managing, for example one tax bill, one insurance bill. 

You want an investment that pays for itself, including mortgage, taxes, insurance, maintenance, and even some money set aside for a reserve to cover vacancies and capital expenditures.

Note the property tax will be -10% on the rent by itself.Month 0 to 24: $2450 * 0.5 - $1573 =-$348/monthMonth 24 to 60: $2450 * 0.5 - $1541 =-$316/monthNext issue is due to the low leverage starting at month 24, the ROI takes a beating.  

Property taxes are also insane.

So, it would then potentially cost you a penalty for early withdrawl and also income tax owed on it.

The 1031 exchange rule to defer your tax is two part 1) reinvest all your proceeds and 2) purchase a property (or properties / DSTs/TICs) with an equal or greater market value.  

I'll save you the details but...Per door cost: $63,300All in Cost: 700kTotal Revenue: 137k(ish) annuallyNOI: 65-73% (in the expenses we included: insurance, taxes, $75/month per door repair expense, management fee 8%, grass cutting, & a misc fund for random crap business license, etc.)Now...