Go here and read/print:
https://www.buellxb.com/forum/showth...B-Buyers-Guide
$3,500-$4,000 seems fair for a pretty clean one, and this looks clean at first glance. It appears to have an aftermarket exhaust (Drummer?), so ask if it has an aftermarket air filter and a tuned ecm. If not, it's an easy fix with a bluetooth dongle and ECMDroid (android only), but can help you negotiate the price down. Check the rear rocker box very well, as it is common to leak (usually on back left). This, if not resolved, can let oil get to the cooling fan and cause a fan failure. The gaskets are easy to find, difficult to replace. The fan is hard to find. Fuel delivery may be difficult to check, but fuel pumps have been going on these lately. Not a huge deal, but something to consider eventually. A guy named "Barrett" sells both rebuild kits and NOS assemblies. It sounds like this is your first Buell, and possibly your first bike. If just the former, please note you will be doing some work yourself. It can be difficult to find a mechanic who is truly comfortable with these, and I would rather not gamble with my bike. Service manuals are available at buellmods.com, and there are plenty of VERY competent members here who can help (just make sure to search first before starting a new thread, most questions have been answered). If this is your first motorcycle, beware. They can be a handful. They aren't the most powerful by modern standards, but the power delivery is strong and down low (insert joke here). That, combined with maintaining yourself could be overwhelming.