I would want to see it working and check their paperwork and serial number on it against that on the machine.
Not even thought of that ... What would I be looking at/for ????
I'm very suspicious of eBay machines. I'm sure many are fine but one lady I know sent a link to an overlocker for me to look at. It was listed as a Janome and had a Janome box. When I managed to zoom in and look closely it was in fact a Jaguar machine!
. Nice little machines but ........!!
And I have seen several people get ripped off on eBay after paying way over the odds for an old machine, like the Orchidea. It is horrible having to tell someone they have been had when their machine malfunctions and is not repairable.
I would want to see the machine working to make sure it does! The machine's serial number should be on the back and I would check it matched their original paperwork, a bit like a car vehicle identification number. The paperwork should satisfy you that it is their machine to sell. (I've seen that little game too).
The Brother 750 is no longer available unless you can find a dealer that has any left. But it isn't likely there will be many around. I was using the 2600 yesterday and it is the same as the 800 but with sewing as well. They are very easy and intuitive machines compared to other makes.
As for offers, a new set of offers came into force today. But I can,t remember what they are offhand!