I purchased then started the remodel before trying to rent.

If that investor hadn't planned it carefully and re-invested that money into the property or even the purchase of another then a recapture fee would hit them hard. 

My LLC is registered obviously, then I received a form in the mail once the property was recorded after purchase. 

It's calculated as the ratio of your total loan amount (loan amount for purchase + loan amount for your rehab) to your total costs (purchase price + rehab budget). 95% is a good target.Avoid application and other upfront/junk fees. 

I'm looking for advice on whether I should purchase my father-in-law's 6 unit apartment in Burien, WA (10 minutes south of Seattle) as my first deal, or perhaps help find him a seller that would pay more than I could and is a couple years ahead of me in REI. 

You get a Capitalization Rate (CAP Rate), which equals your annualized return by dividing the Net Operating Income (you had gross in your narrative) by the purchase price.

With that said, investors have different reasons for purchases.

It was recently purchased in December 2024, which aligns with the timing she mentioned on the phone.However, despite all the communication being professional, I’ve had trouble finding additional information about their business online.I’m wondering if I’m being overly cautious, but I want to make sure everything is legitimate and avoid any potential scams.

If you want to combine two or more lesser sales into one higher purchase that is fine as long as your purchase meets the timing requirements for each sale.  

You can indefinitely defer the tax and use it to purchase nicer property/properties, as well as not have to recapture any depreciation.