I'm currently reviewing some potential acquisitions of smaller client bases at the moment and one thing frustrates me...
I've seen a high number of providers who have a particularly high proportion of annual paying customers which, generally speaking, is not so much of an issue. But most of them seem to have had their bulk of renewals in April/May and looking to sell the business come July. That straight away is going to write down your value, because I have the cost of hosting those clients without seeing a $ for a number of months.
Plus, there's no guarantee after that time they will stay with you too. Just because they're one persons long term client, doesn't mean they'll become my long term client, so I tend to let that phrase go over my head a little when talking to people about their businesses.
It's hard to say. But anything from $5k upwards. If you have some owned IP allocations directly issued from say ARIN or RIPE... then we're talking some more dollars there too.