I would respectfully suggest that you need to be prepared to spend a bit more money to get what you are looking for with no work needed.
A good second hand trailer for a 5m rib is going to cost between £600 and £800
A good fourstroke engine will be starting from £1500 for a small one (30hp) to £3000 plus for a sixty or seventy.
A decent 5m hull with good tubes is going to be £2k plus
Then there is steering, console fish finder etc etc
A good 5m rib for £3800 on a trailer with a decent sized fourstroke engine could be split into trailer ,hull and engine and sold for £5000 plus fairly easily.
I've got a 5m humber with no patches and a 60 Yamaha two stroke, on a good trailer in ready to use condition that will be for sale when the sun comes out for £4000 plus.
With a latish seventy four stroke it would be worth at least £5500