I think they are generally not advisable in most cases and there can be painful (financially) outcomes but they are not illegal.

HOA is always a pain in the neck with the rules and regulations.

Both of us are living in California and know the fun of state income tax and the pain of marginal tax rate increases.  

I feel your pain.

I then put the furniture on craigslist and resold it and I got more for the furniture then I paid because it looked so nice in the new fresh flip.Moving and storing anything for staging is a pain. 

Just FYI - we had self directed IRAs for investing - but we are flippers and that proved to be a total pain in the butt.

Pain in the rear..The buyers broker actually does more work than the seller's in most cases.

Maintenance costs are real and it is a pain.5.)

They also note that the EP permitting process is a big pain to be avoided if possible.One of the contractors initially said that we should probably permit the job just to be safe but then sent me a cost estimate assuming that we'd do the job without permits but added that permitting it would add $500 and 1 month to the timeline.  

I know you aren't asking this, but dealing with different investors is a giant pain.