I must agree with Rawlins that I could only see this working as an after sales/moved in service. There are always clients that want a garden design, pool, patio, car purchase, telephone etc etc and many other things after they have moved in. Normally we arrange all this but sometimes clients want to do their own thing so maybe you could offer some type of one stop shop after service and continually add different services.
I cant see any one paying an upfront fee for a non qualified person to “keep an eye/liase” with a lawyer. Does this mean that the person providing the service is then legally and financially responsible to the person who has paid the upfront fee if the transaction does ultimately go wrong? I could see that the lawyers, whether decent or not would resent and find it really inconvenient that another person is calling them and coming to their office as well as the owner. As most lawyers charge by the hour they might just add this to the bill.
And finally, what if the ideal house is in fact a new build of 300,000 euros with a commission of 4%?………you would let the developer keep it??