4' x 8' for starter's. In the Sac. area you should be able to get your buddy outside for fresh air and sunshine (D3).
Just be sure to provide shade & a cooler area when the temp's rise.
If you haven't seen this yet, it provides a LOT of good Info, Care of @HermanniChris .
Josh and I corresponded last week about making an updated version of the Hermann's tortoise care sheet since the old one we have posted here is a bit outdated and a little too brief in my opinion. So, here is the new one equipped with photos. Look out for the April 2015 issue of Reptiles...
Oh, and Welcome to TFO (Tortoise Forum)
There are a lot of great folks here. Many smart folk's here who know tortoise, and learned by experience what works and what doesn't work.
Take what you may have learned from the pet shop with a grain of salt, as many are NOT experienced tort Breeders/owners.
Ask Questions, were all here to Help!
And Welcome, again ,