What is the best option/mortgage for me? 

For a 1st Position HELOC, it becomes your mortgage.

Allowed to put less than 20%3) lower mortgage interest rate4) proportionally straight line depreciate your property. 

Tax deeds convey title to the purchaser free of all prior encumbrances (mortgage liens, judgment creditors, etc.) of any kind ​except liens specified by Revenue and Taxation Code Section 3712, Lis Pendens actions and any Federal Internal Revenue Service (IRS) liens that are not discharged by the sale”.

The mortgage is fixed cost.  

I have been airbnb’ing it less than 120 days which was helping me to work/ travel a portion of the year outside of LA -  not worrying about the paying both rent and mortgage at the same time.

@Michael Crocker many friendships end over business deals that aren't properly set up!

And I could have lower income in that window after I semi-retire, before my mortgages are paid off to take advantage of a lower marginal tax rate

@Derik Hammer be VERY careful to properly understand your state laws!

Or should I break my promise to get into real estate in 2025 and continue to work part-time while going to college to afford a conventional 30-year mortgage on my first SF and use the "Building Wealth Through Single-Family Homes" plan?