If you decide to buy this machine, you can check with your local sewing machine dealer where you would be getting it serviced and see if you can buy a service contract. That's what I did with a machine I bought over the internet and what I do after my machines are out of warranty. In the Puget Sound area, Quality Sewing has a service contract which costs $300 for three years. In my estimation, it is $300 well spent. Annual service would cost at least $100 a year if I didn't have the service contract and if anything goes wrong I'm sure glad to have it. On one of my machines, I took it in about a month before the first service contract was going to expire and they ended up putting almost $200 worth of parts in my machine plus the time it took to service it and it was all covered under my contract.
Just something to think about when buying a used machine.
As a side note, I have two Brother machines, and they are fantastic. I don't have the Quattro (I have the Innovis 4000 which was a previous TOL Brother). The learning curve for these machines is so easy it's unbelievable. Let us know if you get it.