I don't have any actual dimensions, but you can work from the size of your new 5er. Personally I would like longer than the combined length of the trailer and tow vehicle. Width, enough to open the slides and possible the awning. Height, most 5vers are around 13 feet high so probably 16' more if you want to do roof maintenance in storage. The opening should be at least 10' wide by 14' high, more if there are elevation changes in the driveway or wider if turns have to be made for access.
Of course all this is dependent on the land/property available and the local bylaws and permit requirements.
Ken