Ask HN: How much percent of stake for one joining startup in Marketing role

Hi there, I really need some guidance on how much stake should one give in startup for someone joining as Marketing and VC strategy role. I have no idea if the one joining asking too much stake. Currently he is asking for 12 % stake to take responsibility of making VC fund strategy and getting VC funding and for marketing. The product has gone past MVP and we are doing domestic market launch. We are planning to collaborate with them. Is 12% really worth. On what factors should one evaluate how much stake to be given. Is it really required for collaboration with them or should we go for VC funding by applying ourselves instead of seeking their help.