[gt2]

If the client wants to hire you, then execute the contract by getting a depost, starting the hourly billing, whatever terms you have set together with the contract.

Request access to the github etc. The architecture of code repositories and development process varies between projects/clients, so this is usually on a case by case basis with the simplest being a simple github repo access, ranging to giving the client your public key to get access to their server where the repo exists or code lives, possibly without a vcs at all.

I recommend you commence billing before you look at the code, but I and others have given short free consultations before work begins, so that is an option to you but only if you think it's necessary to win the contract and/or scope the work. If there is definitely work and/or advice to be given, why not start the paid work on a daily or weekly basis.