As a landlord, I can give you two personal examples of the cost to rent in El Valle, Panama.
A small apartment rents for $535 per month, fully furnished, including wi-fi, hot water; everything but your gas and whatever TV package you might want. These apartments have full kitchens and baths and are towards the center of town, a short walk to most everything. They have a nice sized yard with a river running through it, not to mention a pool and a rancho area to hang out, cook out chill in the shade.
Hostel rooms will go from US $15 to $30 per night.