Hi Nanna!
I bought a used Brother 8500 from ebay about 5 years ago. Used it and LOVED it until a year ago when it died. $750 to replace 3 computer boards. Needless to say, I didn't get it fixed and just recently purchased a Singer XL6000. I still have a little Brother 180 and love that one too.

I have nothing bad to say about the Brother machines, but I would be very concerned about a 7500. These machines were made before the 8500s and are probably starting to get old. The parts are not readily available, and if you can get them, they are extremely expensive. The parts most likely to go bad are the computer boards, and I highly doubt they are even making the 7500 boards any more. They're not making the plain 8500 ones any longer, so I was told I'd have to purchase the new ones, which are for the 8500D machines with the Disney designs. Of course, I'd have to pay the Disney price for them too :) Now, that machine could last another 10 years before the boards go out, or it could be tomorrow. Just something to think about. Depending on the price you can get it for, it might be worth it, especially if it hasn't been used much.

My experience kinda burned me on buying used since you have no warranty. The 270 is a great little machine, and good for a starter. The only thing I can say about that is that you will want a machine with a bigger embroidery field in about a week. LOL! Embroidery is addictive. Good luck with whatever you decide and feel free to ask more questions as you do your research. There's a lot more to purchase once the machine is home. Threads, stabilizers, software, reader/writer boxes...the machine is only the beginning.