Why would you need someone to invest 1 eth in your project, what's the use of that 1 eth? Why is it that important? And after that 1 eth, you will give him 500% of what he paid you...does not make sense.
For example 1 eth. It can be 10 eth or 100 eth. Deped on how large our project.
This money will spend to advertisement for good presale.
Its very important for presale and if you sure in project you get 5x.