A person is asking for 50 % partnership in my start-up

Hello, So I started my start-up which has a perticular theme for product line .. A friend of mine has a product related to the theme which he was selling by himself from home on small scale.. he came accross my business and said that I will sell my product under your brand.. so I thought that anyhow I wanted to start my product line so okay not an issue.. and I told him "fine let's do it" to which he said that I will pay for this product as whole by myself. I said fine, since you have brought this product and being a good friend of mine, you make full investment for this product and earn full profits ( I have other services on my business too which I own completely) .. After few days he came up to me and said that he needs 50% partnership in my company since he will be investing into the company.. I have decided to give him the product line only in which I thought that I will invest 50% and he does 50% and share the profits from product line.. (any new product added after the current product that he has brought into the platform) I am not understanding as what should I do . Since he is saying that he wants 50% partnership of the company .. or else if he is investing 60% in the product line thn wants 60% of the company ownership. What should I do?