Here are my thoughts;
1. If you're getting it cheap, it's probably at worst going to be a good learning tool for you. Hopefully you've seen it print, and know the condition, etc. If you're buying a fixer-upper and don't know anything about solvent machines, save your money and buy new. ROLAND, MIMAKI, MUTOH solvent machines are all very similar and require the same care and maintenance.
2. If you plan on doing any long term outdoor signs or vehicle wraps a laminator is a must. Cheap yard signs and banners don't need laminate in most cases - but real estate signs, vehicle magnets or anything that customers expect to last really should be laminated for best durability.
3. If the machine is in good shape, cap top is sealing good and tight, pump works fine, etc.you can let an eco-solvent printer sit for about a week and still be able to clean up the head without too much fuss. HOWEVER, that is only if everything is in perfect shape. I would recommend no more than 2-3 days for good measure, our printers are turned off every night and all weekend. If you're not running it much turn it on every other day and print a small test print or a yard sign or something just to keep ink moving. Do a test pattern and check it to make sure all your nozzles are good every time you print with it.
4. I believe the biggest hurdle is understanding correct file setup, color theory and the materials and settings you must use to print correctly and achieve good results. If you have none or little background in printing or prepress in general you have a lot to learn and it can be a daunting task with a steep learning curve. It isn't like buying a desktop printer and plug and play...to get good sellable prints you need to know how to fix and tweak colors to match your customer expectations. You also need to understand resolution and how different types of graphic files should be used and when to use them. Then you have to learn all the materials, calendared vs. cast, when to use what material for what application, etc. All of that takes time and experimenting on your dime.
In the end, I know everyone thinks a printer is a great thing to have, but unless you can average about $5,000/month in sales minimum, you'll be better off subbing out your prints to a wholesale vendor and skip the cost and time needed to maintain a solvent printer.
Again, just my opinion - I wish you the best of luck in either case.
