That starcraft should be in your driveway. What's the holdup?
I would buy it, run it as-is with the 15, but maybe keep an eye out for a 60-80 hp. If you want to plane with a whole family in it, 60 is about the minimum. Might get there with a 50, but it depends on how many twinkies your family eats, if you catch my drift. Also, if your family ever wants to learn things like skiing, I would go 70 minimum
Pros to that hull: Once on plane, it is pretty efficient since it is basically a flat bottom. It's also overbuilt with generous ribbing and stringers so it's a good solid, rigid hull. Floor replacements are pretty easy by comparison. Cons to that hull: The flat-ish hull means that if you do have enough power to plane, it kinda slaps the tops of chop and wakes so it's a bit crunchy.
So... I would personally approach it like this: buy it. If you discover you want to hit non-10-horse waters, either look for a 70 horse, or look for a more inspired modern hull with a larger motor on it already.
If you end up with a pontoon, just be aware that they are incredibly inefficient. Those fast pontoons you see don't really weigh much more than a traditional boat, but they sometimes need 150 hp to overcome the awful, round pontoons and get the same speed as you would get with a 70 on that Starcraft.
You'll run into a question at that point... do you go fiberglass, or do you stick with aluminum? Aluminum (much like wood) doesn't do compound curves unless you spring for one of the fancy hyrdro-molded hulls. Fiberglass CAN (not always) net you a hull that compromises less. By that I mean they can have more better qualities and fewer trade offs - dryer (less splash in), nicer ride but still efficient, easier planing with less power, etc. Of course, depending on the hull design. It's just that with fiberglass, the hull designer has the freedom to engineer it how they want a little easier than aluminum or wood.
But the important thing is... That starcraft is a SOLID starter, and looks like a good price. The outboard alone is likely worth $750, at least around here.