I had a customer whose company manufactured big floor cleaning machines; the sort you see in Tescos; and he wanted me to be a salesman for him, where he would provide the transport and I'd have to go to various parts of the country on an ad hoc basis and give a sales display. He would pay me a flat rate; something like £60 per day, plus what sounded like a generous commission on anything I sold.
I quite fancied it, it sounded like it could be a bit of fun to be honest (I'm a show off attention seeker by nature), but I declined.
I'd probably only end up with the £60 and no commission some or most days, and I can do a lot more with window cleaning.