This is what I have found in my area.(Upstate,SC)
early 80's 25HP outboard running-$700 to $1500
Older jon boat-$300 to $1200 depending on condition,lay out,riveted or welded,and included gear
12 to 16 foot trailer good to excellent conditon-$500 to $1200
12 to 16 foot trailer fair to poor condition-$100 to $500
As you can tell,prices vary widely.If you wanna buy and go fishing, without putting work into the boat,you'll pay more.Take into consideration the future usage.Will you be out once or more a week?This would be worth a higher price.Would you only be out once a month maybe a few times a year?Lower price would be easier on the mind and wallet.If you're looking to build, go as cheap as possible,if you're ready for a hull out redo.If you're looking to just arrange the interior to suit your style,spend more for a hull with nice paint,no leaks,and a solid inner structure.There's a lot of factors to buying a boat.Look around your area,classifieds,Craig's list,and ebay.This would give you an idea of a price line.With what you described,I would offer $800-$1000.If the condition of the trailer,hull,and motor is in fairly good condition to excellent,I would go as high as $1600.For me to go over $1200,the boat would have to be ready for the water.It doesn't have to have decks,seats and all the add ons.It just has to be ready for the water.I don't know if this will work on this forum,but we have some good guys here,so it might.Talk to one of them and get him/her to go with you to look at the boat.You can get an honest unbiased opinion.If you're around upstate,SC,I'll be willing to go with you to check out boats.Good luck.