Depends on each owners personal situation.  

This depends on many factors, including the frequency of flipping transactions done by your Solo 401k.

It varies so much from state to state. 

Let me know if you need advice on some of the meetups, I've been to most of them, some will be more helpful than others 1 depending on what you want to accomplish and 2 where you are starting from.

And depending on the amount I take out my cash flow from my first(current) rental may pay for those monthly payments on the heloc.  

Lending laws will vary depending on states, which I'm sure you know. 

@Andrew Horowitz the rules for tax lien sales vary from state to state and sometime from county to county. 1) tax liens are virtually always first sold at auction.

It depends on your taste.

I was more so looking at a buy, rehab, and rent situation, with the possibility of flipping depending on the metrics on the buy.

. - cap expense: it varies more by size than value.