Sure the big team is needed if you wanna build big company, but you can start as a solo developer. I think you have very low chances to attract investment if you will be alone and will have no product, but you can try! May be someone will like you idea and you will get some investments.
Look at Elastic. This project is made by 2 people and now they are on the stage of testnet. They did it, so you also can! May the force be with you!