I need help with hiring a interim CTO

Hi Guys,
Our CTO aka my brother will have to leave our startup for a year, because he will join the army. We have found a potential CTO for that period to can take over from him. We don't have any money we can spend, so we will have to give equity to the interim CTO. The platform we build is done, and her job will mainly consist of fixing bugs and some small changes. What are some recommendations for the terms to agree upon:how much equity do I give her, when does she get the equity ? Considering my brother will return after that year make this situation difficult. Any advice is appreciated!