IMHO: hold onto it!
It's a fantastic little engine (with a ton of torque)
unfortunately most have been replaced by stinking predators (or other cheap clone engines)
and still they are highly underrated since you cannot mod it as easily and/or cheaply as you could with a clone..
Still, for a stock engine it outperforms all clones of similar displacement (yes that includes a so called 7hp predator!)
maybe not in rpm, but surely in torque.
And what's more.. they're reasonably cheap to find
(as said above many replace them with clones thus used 5hp are plenty)
so you don't get much if you're trying to sell it... 30 maybe 50 bucks if you're lucky.
And to put in in another perspective:
If you pay me a new clone I still wouldn't sell you my 5hp briggs (which is in need of some TLC)
'sid