investor puts up half the start up money and you only give them double their money back? no you must give them part of your company.
That does seem fair, I would be willing to negotiate for a stake in the company. I believe 18% would be fair. What are your thoughts?
Since you don't understand how real business work, I would like to know how old are you? I mean if somebody puts 50%, then investor should have atleast 50% shares of company otherwise this looks cringe. Your math have no sense.