It all rather depends..
on how hard they thrash it, how often they thrash it, what they are supposed to be doing when they thrash it - and of course being a 210, and especially if private hired they'll probably crash it.
Basically you could probably reckon on (say) $4000 for a 100hrly, with the occasional one at $10k +- might be less in private use.
Insurance would be higher for training and charter but depending on the value, the amount of public liability, whether you need passenger liabilty insurance for Charter or not - say $6000 upwards, maybe $12K or more for a really nice late model.
Engine is 1700 hrs(?) life or 12 years in Charter and about $50-60K to overhaul, prop about $16K to renew or 4K to overhaul -either 1500 or 2000 or 2400 hrs or 72 months in Charter.
Hangarage at a place like BK - probably $400/ month, then about $15? per movement (keeping an aircraft on line will give you a few of them!)
Fuel? 50-60 litres per hours again depending on what they do with it - maybe hire it dry to them ?
Don't forget you ASA Charges - about $18 a time at (say) BK
You should also add something for wear and tear - a paint and interior job can easily be $25K and with some operators, you will need one about every 5 years or so.
Work that lot out and you'd be nuts to put it on line for less than $300 per hour - many desperate owners who put nice aircraft on line are of course! for sure if it gets the big hours you need to offset the fixed costs, it will be a wreck quite soon - one way or another. The truth is when you work out what your real costs are and try to equate to what they are paying, it wont work.