Hello Diane
If You want to put in gas and elec you will need a permit to keep it legal in california.For gas anything over 3 feet long has to be inspected.The patio will have a natural grade or slope away from your house so drain in that direction.I agree with Aaron if you plan on moveing keep it simple attach with anchors to the slab they are easy to remove and repair.If you do it pm me and I will install the gas and elec leagel,all you have to do is put up with my 4 kids!I would like to bring the wife and kids they are a great help.seriously i have alot of experience in elec and gas it is a huge part of my job.I know cali code and will help with the inspector.Any help you need and all you have to do is deal with one contractor!!!
Jason