Stephen, You have got to go see the boat and check the usual things. You had a boat before so you should have n experienced eye. Check the hull and deck for cracks chips and grazing. Check the console condition, electrics, battery, fuel tank, fuel line, steering system and steering cable. Have a good look at the tubes and check all the valves. Pull at the seams especially around the transom and bow areas.
Check the engine or get someone to check the engine for you for condition, corrosion, mountings prop shaft, compression, spark etc.
Don't forget to have a good look at the trailer.
Get a sea trial.
Remember all the little things that need fixing add up to a lot of money. Build all the repairs, engine servicing etc into the price when you make your offer and hold out for the best deal.
The Seariders are a practical workhorse type boat and can stand up to a lot of use. Most people on this forum have nothing but praise for this type of boat.
I hope it works out for you otherwise... Happy hunting.