my best expence was 50p.
i gave customer 50P off for recomending a friend (this deal was targeting my 2up 1 down houses)
in turn she recomended a £10 house
neighbor of new house came out hers was £6.50
She then had me do a £60 hostel she worked at
and a £55 hostel part of the company all are monthly
then annually i do the hostel charitys community centre which is £80
so 50p made me an extra £1658 a year
funny thing is i still do them all except the lady who recomended the customer to me