You can start a small projects with any amount, all you have to do is create an idea that gives you a trademark. Because all clients or investors are looking fresh and newly idea that excel in the crypto currency community. If you do that you don't need to have a capital for the projects, because the sponsors are willing to provide you all your needs for your project.
You cannot say any amount. It all depends on the kind of project and the budget it needs to start no matter how small the project may seem. One thing is confirmed, starting little is good and it can be built from there but whoever is going into any business will still have to be realistic to know what he actually needs to kick the ball rolling for that little start without flopping and building it from there.
I believe any small amount also will be enough when we are having a new innovative business idea as more people will be ready to contribute when the idea is good so they will help a business to get built.
I think for me just 3 to 4 bitcoin are enough to start a sound regular business in my country because the price of one bitcoin in my country is about 460000 in my local currency and 3 or 4 are enough to start with these bitcoin values. But to start any business I will prefer to hold my bitcoins in my wallet and Walt for some more time and wit for the price to go up more and I earn more money.