Sell or hold sudden windfall property

[Marie M.]

Just moved out of a primary to convert it to STR and realized the value is significantly higher than it was 2 years ago-- I think it's a bubble, it was worth 300k and now it's worth about 700k.

Will cash flow 50-60k a year on it as a STR which I'm setting up right now. So it would take 8 years to recoup the current profit of 500k.

Our goal is to acquire cash flowing properties, so selling one wasn't even a consideration until I realized the gain that was possible all the sudden.  
The other big plus is at this point, we have lived in it and would not pay capital gains tax. 

The downside to selling is I'm attached for other reasons it's a unique, one of a kind property-- and it's my SHTF option.

Any thoughts or insights would be appreciated!