Baugo;
The previous posts are valid advice.
Less than a grand is pretty cheap entry to micro-roasting. If you can "road test" the used Sivets before buying, you should do a couple different roasts with green you are familiar with.
Call Mike Sivets and ask for his input and his estimate of refurbishing and startup costs.
The commitment, skill, and palate of the cupper and roaster person make a bigger impact than the particular machinery. Having some experience with dozens of different espresso machines and different coffee roasters and roaster controls, I am convinced that virtually any equipment in good working order can produce creditable coffee. Exceptional product comes with exceptional commitment, aptitude and skilled experience. Excellent equipment with useful controls that allow repeatable production will make the pursuit of quality easier.
My experience with fluid bed roasters was similar to Diablo's for resulting cup characteristics comparing same green roasted in drum roaster. I also tend to prefer the dark roasts and espresso coffees from the roasters using drum roasters vs. fluid bed roasters. That said, any cup profile can be modified SIGNIFICANTLY by subtly (or dramatically) tweaking the roast profile (temperatures/heat transfer rates) in virtually any commercial roaster.
Folks naturally tend to be extra committed to the concepts they invented or paid for. Therefore some spirited discussions will rise (check any forum) about the subtleties between equipment.
Find equipment you will be comfortable and confident using, learn it, train on it, pay for the factory courses, pay for the skills courses at conferences (like SCAA, CAC, NCA, Coffee Expo, Coffee Fest), hire a consultant or several, take a course from a professional training operation, roast on the equipment you are considering (at the vendor/manufacturer/satisfied client), buy and evaluate coffee from your competitors, cup coffee with your green coffee vendors. Put the information you learn to the test (not all advice will be valid for you) by roasting and tasting comparatively with your standard practices.
Baugo, you have been asking a lot of questions, and received a ton of useful feedback, but you will gain more from hands-on roasting practice and comparative cupping. You will also have better informed, more directly useful questions and responses if you do a bit more basic research. Read Ken Davids' books (Coffee and Roasting), Kevin Knox's book, Ken's coffeereview.com take a course or two or ten. Do searches on forums and read the "back issue " threads, other people have already done all that you are doing and have discussed and asked the same questions already. Go to the coffee conferences, take the workshops. Hire someone experienced to roast with you on your equipment and cup the coffee with you. If you are planning to buy an Agtron meter or controls, buy it now and take their training program (same for Diedrich, etc.). If you don't have the cash to pay for training, do all the "free" reading. Then spend $100.00 buying coffee from several reputable roasters and comparatively cup them with your products.
All of this will make a much more significant impact on your roasted product quality than the particular roasting machine.
I admire your thirst for knowledge and pursuit of interesting coffee experience. I hope I only rambled and did not rant. Best regards, Bill