Hi
I have always used biotherapeutic micro current . I started with their first unit back in the nineties and now have their more recent ultimate unit.
So that's one company to look at.
Another leading brand is caci - very famous but will cost you a lot more.
When teaching facial electricals in college we used to use the goddess system (pads on lower face, micro current probes on upper face). This is s much cheaper way of bringing face lifting into the salon and the results were pretty good actually.
There are some other brands like ellisons and Carlton that do this sort of unit too so shop around.
You could consider a serviced second hand unit but you would then need to do the company training.