Seeking Advice on onboarding CTO to our startup

We are 3 co-founders (Sales & Operation & Product) in the B2B SaaS business, we already have launched our beta (more than MVP) and working on acquiring our early adopters' customers, and because we are bootstrapped we can't afford to continue spending on the development without any fund, and for scalability, we need a technical partner, initially will have equity solely without salary and will be part-time, after getting funded or have good revenue we will offer him a salary and onboard him as full-time.

We currently have 2 potential technical co-founders to choose from, we agreed on a 2 months probation period to test them, so we have currently two questions:
1- How much equity should we give him at this stage?
2- shall we grant him access to the source code and start working?