I would be surprised if renting came out anywhere close to ownership costs for 40-50 hours a year. Yes, you won't always have the convenience of flying on a whim, but good planning and met appreciation can alleviate some of that nuisance.
Say a commercially owned R44 is operated for 200 hours a year, if you rented it for 50 of those hours, you would only pick up 25% of the ownership overhead costs (hangarage, long term maintenance etc) in addition to the direct operating costs. If you own it you are picking up everything, and as other point out, you will still get whacked on calendar maintenance ops with a low flying rate.
You should get some professional help from someone in the operating business and do a full cost/benefit analysis if it's about money. If it's about saying you own a helicopter, then you should probably buy one.