Asking people to move to San Francisco for 3 months is just a tad bit crazy/expensive don't you think?
One might spend ~$5,000/mo for a short 3 month stay in San Francisco.
Why not organize accommodation for them as well? Renting a house for 3 months over a summer and dividing it by 3-4 grantees would be cheaper for both parties. And it would help manufacture some incredible collaboration as well imho.