Hi Everyone, My name is Moustafa and since my wife and I just got married we are looking more into our future to be FI.

If they get married it will help her earn SS benefits, etc etc. 

My fiancée and I are getting married in November and will be moving into a different rental in another part of town shortly after.

For reference, I am 30 years old and not married.

This defers capital gains and depreciation recapture taxes on the sale of your fourplex.After converting it into your primary residence, you may qualify for the primary residence capital gains exclusion ($250K single/$500K married), but only for appreciation after the conversion; gains from the rental period remain taxable.

At the time, I had just graduated with a physics degree, landed a great job in the Bay Area, and was newly married.

Similarly, the sale ($575K) minus your adjusted basis determines your capital gain.You may qualify for the primary residence exclusion (up to $250K single/$500K married) if you lived there 2 of the last 5 years.

If the client is in CA the community property state laws may help here (not entirely sure) depending on when the property was acquired but it would be a great question for an attorney as Jason mentioned.If they were married and went through a divorce it would be worth looking into how the divorce paperwork stated how that property would be handled.

An example of a mistake was a line item for alimony that I found on my taxes (I am single and have never been married).

This exclusion allows you to avoid recognizing up to 250,000 of gain (500,000 for married couples) on the sale of your primary residence.Regarding your investment property in LA, it does qualify for a 1031 exchange.