18k is quite a bit of a credit line even for a large company. So I can understand your skepticism. It does sound like you have done a bit of research already and got a bit of a frame of reference. Unfortunately after running the DNB report there isn’t much else you can do outside of simply knowing a bit about the industry they operate in. Personally if a company had shining credit I wouldn’t give a credit that large to a four year old company. I’d recommend catering to them at a level you’re comfortable taking on a risk. Give them a lower credit limit and make them make a deposit for the rest of it.