There is little first-hand knowledge here about working girls in places like Tamarindo because most of us don't go looking for working girls in places like Tamarindo. Tamairindo is a surf-and-beach tourist area.
The best way to find P4P in places like Tamarindo (or San Isidro del General or wherever) - IMHO - is (a) Badoo and (b) Tinder; but you need to play a long game (start a couple of weeks out). It's a risk because they might be fat or whatever.
If you have time, you can find girls that need rent money or food money or whatever money. But it takes time.
The Hotel del Ray in San Jose or the Cocal in Jaco or the Sportmans Lodge in San Jose or any of the salas (MPs) is point, click, discuss / negotiate and go.