I just want a bike to cycle around and to be strong enough to give an occational lift on the rear rack.
The only reason that I want to keep the budget down, is because it might not get used every week, and it will be chained up outside, at risk of being stolen.
I have my present old bike, and folder chained up to an old lawnmower. The link above is the first one I came accross.
Unlees you can get some documentation that says the rear rack is suitable for passenger duty, and carry it with you, there's a very good chance some "shiny buttons" constable is gonna ticket you for "2 on a bike" Some foot pegs would be good for that too.
It's pretty crude bit of kit, but that's what it's meant to be, 40 lbs, one piece crank, straight tubes, should be a tough bike.