What area or field are on in ? Depends.
Assuming you already know what kind of start up I would suggest trying to save money from your "9-5 job" or use the skills you have to set the basics of the start up by offering your skills relevant to it. In that way you also build up a portfolio.
Last but not least you can ask for help from different funds within EU and your country depending on which country. They help start ups with certain basics costs.

It's a bit tricky giving you more relevant tips without more context.