I would highly suggest a credit union or regional bank.

Would a unused, open HELOC affect my credit worthiness or increase the risk in the eyes of a traditional bank lender?

His primary mortgage was sold to a private lender in the early 2000s and he claims he had to give an explanation each time as to why he financed with a private lender with such poor reputation every time his credit was pulled.

And then sell your current primary - take that money tax free to pay for college. 

Feel free to network with Todd or other members via other threads, or other parts of the site.

You just need to have a current housing expense meaning you cannot be living rent free.

If you purchased from the party who purchased at the tax sale you probably would have received a SWD because the Grantor would not have wanted to warrant anything other than the Grantor's actions.While I'd be surprised if a county employee opined on the status of your title, there may be a difference between having a clear title (one without a current challenge) and insurable title (one free of significant possible risk of being challenge in the future). 

We've been car-free for many years and want to avoid owning a car as long as possible!

Will,That's a question that involves a lot of detail and conversation to map out the LLC, Financing, Grants, and percentage of partnership should you decide to acquire more than 5-10 properties.Feel free to reach out if you want to discuss the scenario and I can try and detail some tips from my experience. 

I will continue to invest in California because of the high appreciation and high rental income.I hope this helps and if you have any questions on how or where to find some deals, feel free to reach out!