Everyone gave great advice and its tough to choose.

Me personally all the machines I have purchased I wanted and researched and one day I plan to have a big big room to put all of them in. I needed some cash a while ago but could not take myself to sell them. IF I had a machine I bought and not fixed up I may sell that but

1 - All the machines I have put a lot of work into and to get your money back is tough.
2 - Pins are on the rise so if you sell key titles and want them back you will have to pay much more and may get less.
3 - How much enjoyment do pins bring you. To me I love looking at them even when I am not playing them, I like working on them and of course playing them.

Sometimes weeks will go by before I play any but like all hobbies you take a break.

I do not know your situation but I would only sell pins you do not care for OR are b to c list games your not super crazy about.

For example I have a Taxi and it was one of my first pins and I rarely play it, when I hear the tune and see it, it brings great memories of why I got into pins.

Good luck on what you decided. Remember you can ALWAYS make more money, finances are always a timing thing for the most part.