whether rent or buy, you need to factor the cost of gears into your charge.
let say a piece of gear is $1000, usually rental cost is about $35-$40 per day, you need x3 and factor that into your charge, why? you need to make a trip to collect and return, time is money, in case you not free to collect a day before or return on the next day, additional cost will also involve too.
if you decide to buy a piece of gear, the cost is $1000, you need to add 50% of the cost for maintenance and repair, the gear will have to write off and replace after 3 years. So it is $1500.00 in total 3 year life span or $500 per year.
let say you will need it for 10 assignments each year, it will cost you $50.00 for using it on each assignment.
so it is make perfect sense beside just charging for your labour, you will have to add all the expenses into your rate if you plan to do it freelancing or full time.
there is no such thing as shooting for FREE, that is only applicable on the receiving party, on the photographer side, it is always 倒贴.