Thank you for taking him in and giving him another chance. I would let him get used to you and the new house for awhile before I would get too involved with the training. See how he is and what he needs work on, then start with the basics, he will learn.
We have a 3 year old rescue, Brutus. In his short life he was passed from home to home and never has been told No. We made sure he was integrated with our house before we took him to training classes and it is never too late. Just have extreme patience. We still deal DAILY with brutus. He's total boy and does what he wants despite being told no. He's getting there but the road is long with him. Brutus is very smart and learned his commands but he decides what he wants to listen to. Good Luck!
Great advise above, also set a certain amount of boundaries and start a routine right away. Bulldogs love routine and it will help reduce the stress levels. Mainly feeding times and potty break times /walks should already be set in stone as those will be most of the routine they will look for.
Don't overwhelm him and just let him sniff around, maybe give him a place of his own until he feels comfortable to roam around, maybe a crate. Give him boundaries to get used to everyone and everything. Let us know how it goes and share some photos!
Hiya-first of all you done wonderful thing taking on a unwanted pet - i would agree -let him settle -but if you are planning to put any rules into action do it straight away so it wont confuse him - for instance -no sleeping on the couch etc
With obedience training - you can start leash training and simple commands -like sit ,stay pretty much straight away -and dont forget treats :-)