My advice is to look at it weekly.
however too many variables to put a value on it.
if you had 200 houses all on 1 road at £10 a pop then £2000 a week is achievable ......... if you have 200 houses spread over a 5 mile radius then £2000 a week wont happen.
only you know your work and what is possible
if I were you I would agree a weekly target with the employee and tell him if it takes 4 days then fine if it takes 6 days then he has got to work a Saturday ........ assuming its a fair target ,,,, like I say only you will know that
but Richy ................................................ you know all this already