What should I do? Finance & Investments & Business?

My parents died a few years back and I got around $20,000 for their deaths (usable) and another $30,000 in some kinda realty investment that my grandfather put my money in. What would be a good way to have my money increase, I want to be able to afford a house in 4 years. I was thinking about saving $10,000 of it in my 0.75% interest account and figuring out something to invest the rest in or maybe buy start being a merchant on ebay. I am a college student and my school is paid for and I am only 18, any ideas?