At least you are being honest in that reply you send someone out to clean it so you don’t pretend it’s good work it’s just turnover, if you need work on mass you need to leaflet drop or use this lead method but the work will be hot and miss,more miss than hit though.
Thing is though you say they just want to sell you leads and dont care what type of house or customer it is, and that you could end up with work you dont wan't.
Thats only true up to a point. Lets say i do lead generation for a new window cleaner, i know for a fact he wants work and growth so will literally take any customer that comes in, however an experienced window cleaner already making decent money maybe just looking to top up his round slightly will be more picky, doesn't want terraced houses, flats, awkward access jobs etc. He is more likely to look at certain leads and go, right im not doing that, chuck those ones in the bin.
The most important thing i have found is ROI - Return On Investment. How long it takes to get your money back from paid advertising.
Door Knock Canvassers - Will take 3-5 months to get your investment back paying for a x3 clean
Leafletting - I'm told with mass leafletting takes anywhere from 4-6 months to get your investment back if done properly
Lead Generation - Will take you 2 months almost guaranteed to get your investment back. Even if you are super picky it will only take you 3 months max to get it back, so its still more cost effective than other methods.
Lets say Myself or Adam sent you 20 Leads for £10 each @ £200 total. Even if you just converted that into 7 customers at average price of £15 thats = £105 Monthly turnover That's a 30-35% conversion rate which is extremely low by the way most people can expect 50%+ each time. Within 2 months you have your investment back, you are now in profit and any customers who you are not 100% sure about you can dump knowing you are not losing out as you already have your money back and just keep the best customers you gained.
Now lets say you are very fussy and don't want any jobs in certain areas, or flats or terraced houses or dodgy parking. It's simple, you can afford to be picky and choose what you want, so simply dont convert the leads for those types of customers and just convert the good ones. Your numbers will be slightly lower, but in most cases by being picky you will now go from getting your investment back in 2 months, to getting your investment back in 3 months, and on your terms, you've handpicked the customers you wanted and still get your money back within 3 months which is still on par if not slightly better than Door Knock Canvassing / Leafletting.
I'm not telling you all of this to try and convince you to use or do Lead Generation at all.
Like Adam above, i just like to be honest and share personal experiences of what is realistic generally speaking. You can fine tune Lead Generation to work the way you want it to work.
All that matters is Quality of customers and return on investment. If you can find the right balance with both of those things with lead generation or any type of advertising then you are onto a winner!