Matt
My costs on this would be:
50,000 leaflets = £480 print only (A5 single side)
£28 per thousand delivered (to areas of your choosing; VERY IMPORTANT) = £1,400
Total for print and delivery £1,880
From this I would expect:
0.25% customer calls = 200 custys
Averaging £18 per house = £3,600
Including SFG cleans 15 houses at £100 each (extra) = £1,500
Total income approx £5,100.
Obviously depends on time of year etc etc.
I would expect to lose about 20% of this work over the year (natural wastage and I get fed up with time wasters!)
As for the design, that's the clever bit. Why not get yourself a graphic designer to do them for you? Give them the problem, that's what they should do. £200 should sort it.