RE has always been a big thing that always intrigued and in 2024 I went ahead and took the risk of buying a fix and flip investment with a partner and soon it will be on the market!

The guru your son is learning this technique from is likely not telling your son that the deal will almost certainly encourage your son to get an "off-market" deal from a "wholesaler" who is unlikely to properly disclose the details of the property or encourage an inspection. 

Quote from @Mo Karim: How are the Milwaukee burbs market?

My lawyer suggests in a situation like this that I give them a notice that I am the new owner and that as of a certain date they owe market rent of $X,XXX.

In my area these are rare so they are difficult to set market rent, and I imagine get a lot of wear and tear with a lot of occupants living there. 

Personally, in this market, I would work on saving up and really doing my best to find a great opportunity and pull the trigger then.

There's no precise figure because no one will understand your STR or market as well as you do- or, as well as you will (with time).

I am looking to do AirBNB Arbitrage in Lancaster area as it is the closeby market to me.

You can contact some local property managers and get a better idea of the rental market.

@Martin Manning To add onto what others have shared, in the most simplistic terms, apartment complex values are based on Net Operating Income, or NOI, and the cap rate.Price = NOI / Cap RateSo, if an apartment complex has an NOI of $100,000 and a market cap rate of 10%, the value is $1,000,000.Listing agents for complexes love to price based on a pro-forma, which is utter nonsense (unless you're in Austin, in which case apartment complexes apparently have floors made of gold).