Oftentimes people get into a 401k vs real estate conversation when it isn't really the fact that a 401k is involved that is problematic, it's the restriction to assets that don't perform well and/or have terribly high fees relative to those returns, as you wisely mentioned. 

There's no 20% restriction, only for FNMA reo resales.

That is true here to, you have to subdivide, with a minimum 30' deeded access, among other restrictions.  

Canada has a lot of restrictions on what you can do with your self directed retirement accounts so while we have Canadian private lenders, the funds are their own, not from their retirement accounts. 

You can also put in clauses in the contract that restrict the owner from taking out liens on the property, but that isn't a for sure thing.If you get a traditional loan for the property as a personal loan?

As @Tom V. mentioned many banks will offer them but there are additional restrictions in Texas and with different loan programs.  

There was also nothing written in the declarations about rental cap restrictions; my plan was to BRRR. 

There could be some restriction about this but I don't personally buy properties to flip, I currently only buy and hold.

We've been near 100% occupancy since the restrictions for vacation rentals were removed. 

An overlay is a requirement set by the lender that is more restrictive than Fannie/Freddie guidelines.