Actually the build ratio if you dont have the downrange safety factor is 2 to 1 this is right out of the book
Maximum Firing Distance
Minimum Backstop Heights
15 m or less 3 m
25 m 4 m
50 m or more 6 m
so all depends on the legnth you want to shoot from I know most ranges are only 25 for pistol.
I know this as I am in the process of getting my land approved, heres the list you will need
1st off 2,000,000 libiality insurance spefic to the range, lots of dirt, fenced in proptery, signage, the biggest one is getting the ok from the county, you have to present the operating instructions, rules of your range, proof of insurance, drawings, pay the fee then they put it in the paper for 2 weeks, and they speak to each neighbor adjecnt to your property, Some people say is it worth it? well I live over an hour from calgary so rather then driving to the range and waiting for them to open or have a lane I can use, I can go out to my land and shoot when I want. So yes it's worth it. Still getting a club membership to an indoor range for the cold and wet days.
Hope this helps you out