Contribute to HSA the maximum you can, then invest to get the best possible returns and wait.

Possibly!

I heard a story today of a condo owner whose entire complex was lost.

Is it possible to avoid taxes on the gains if I buy another property for $564k ($900k - $336k) and make capital investments of $336k?

You don't want to overstretch on the first one.In terms of evaluating quality deals, you won't know what those are for a while so you want to get as many reps looking at properties as possible.

I’ll try to give as much helpful advice as possible. 

All these properties were purchased for under 100k (not possible now, we got lucky with the downswing of the market at that time).

My original plan was to find a 4 plex in california buy using fha loan, move out after the first year and generate cash flow and appreciation, but after looking at properties it became clear to me that’s not possible with todays market and interest rates.

Whether it's through sustainable practices, adaptive reuse, or innovative space planning, the possibilities are endless. 

Through the LLC structure it is possible to take advantage of the existing mortgages modified first at 4,125% 22yers and 1%, yes one percent, for 40 years.