Well this depends.
Is it a "NEW" model? The new type are VERY competent in seas, even the 13 foot model. The newer model has a conventional bow, with a semi-V hull.
The older "Classic" style 13', the one that started out in 1958, is also a great skiff, but it is essentially a flat-bottom skiff and while unsinkable (yes!) it will give a bit of a rough ride in a chop.
If it is an older model, be sure that it is actually a Whaler--- and not a fixed up copy (it happens a lot) and also be sure the engine is the right shaft height. Older models (blue interior) are mostly "short shaft" or "standard" and need a 15" or 16.5" (old measurments) length motor. This is recognized by the cut-down stern motor mount area. Newer models use 20" shaft motors.
You should have at least 20 hp. A 25 hp works great. There is little benefit from any more power-- you will not go much faster (who are you racing anyway) because the boat stays flat- with all of the bottom in the water at all planing speeds, but you will be able to pull up an adult waterskier easier with a bigger motor--- if it is on there. The mfg rating is maximum 40 hp for the classic 13.
Remote steering is nice to have--- but plenty of the older ones use a tiller handle on the motor.
Older short-shaft models tend to work best with the original style cable and pulley steering, because special mounting is needed to put Telflex type on because of the transom cut-out. Long-shaft model boats will use the Telflex steering fine--- with the push-pull cable mounted directly to the motor.
If you get an older used one--- the BOAT holds its value with no depreciation, even some appreciation. The hardware--- like motors and trailers are subject to depreciation as usual.
Many of this model have a rail along each side. SOME have a bow rail which I personally find "in-the-way" on this boat.
A very nice thing to add would be a simple "bimini" sun-top. Especially for the Florida sun.