It all depends on the year and what comes up. Could be 3K on a bunch of little things, or a big thing like bottom paint. Look at the zincs, sanding and refinishing of wood components, new chrome hardware in places, cushions reupholstered, parts and service on the motor, electronics, work on the trailer (tires, brakes, axle etc), replace soft spots in the floor, transom rebuild (switch to a pod?), quality batteries...
Some will be needed every year, some will rotate in every few years. $3-5k average per year would be
my guess.
I have barely scratched the surface on the list of things that could use attention now, or may need attention within the first few years of ownership.
I kept things simple and found a 2002 17.5 ft G3 aluminum with a 70HP bomb proof 2 stroke Yamaha. Even this can get expensive. Nickel and dime to death.
Oh, take a look around here, these guys are SUPER knowledgeable and helpful when it comes to fishing our waters;
http://www.sportfishingbc.com/forum/forum/sport-fishing-bc-forums/boats-motors-trailers-and-towing-rigs-forumOftentimes they know the story, the previous owners experience with the actual boat that come up for sale. Sometimes they have great things to say or know the seller as one who cares for their stuff, other times they know of pitfalls about the boat after already taking a look at it.
Those Crestliners are cool, and hard to find. The inboard will be thirsty, but are pretty easy to work on. Think of it as a car engine from the 1980s.