yep very good idea, the people that do the garden for my misses parents charge around 50 quid every 2 weeks and they are in and out in 2/3 hours.
EDIT where is he based?
Dunblane (near Stirling)
TBH, I helped him through the uni summers. While my friends worked for investment backs and earned good cash for long hours, I worked less, enjoyed it loads, was outside and still earned reasonable pay. Don't worry about working outside in the rain, unless you have to earn every single dime then usually you don't need to since many jobs are not safe or practical in the rain in any case.
Other common jobs included assembling sheds, painting fences and sheds, re-turfing, erecting trellis, removing small trees, spraying weed killer, picking apples form trees, resetting paving slabs, making a sand-pit for the kids, etc.
Most of this stuff is very easy and a builder would do a great job.