Weigh out his worth to the business - is he bringing a skill that you severely lack? if so you need to think about what you would do if he left - could you replace that skill easily? If so offer him less equity
Investing money is amethod of purchasing assets in order to gain profit in the form of reasonably predictable income (dividends, interest, or rentals) and appreciation over the long term as well as short term
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You need to look at how much he's investing compared to you. And then the levels of relevant expertise you both have and how each of you will be contributing to the business.
Both Venture Capitalists and Angel investors are risking their hard earned capital by investing in your venture in the hope of long term returns that are worth many times their original investment.