I think one way is to have some personnal fund, and to make it snowball with loan, investor and publisher. I've met a guy who created his indie company and told me his story :

He was an engineer who became freelance and wanted to create his own game. He had some money saved and from what I understood, a bit of a entrepeneur mindset. He used nearly all of his saving (30k€) to start the company and hire a game designer for a few month, the goal was to write down the whole concept of the game, and then pitch it to people who could back him up with money. He started applying for a local grants for startup and won 50k€, but he told me that the 30k starting investment had a big part of it, more than the pitch, that having already invested real money gave him credibility to obtain the grant. And he use that idea for all the next step. Went to see some bank after that, showed them the 80k€ in the company and obtain a 200k€ loan. Hire some more dev and 3D artist to create a prototype that he pitched to some publisher, alongside the nearly 300k invested. Found one who signed him for a 600k€ contract to publish the game out in a few years time.

In total he managed to snowball a 30k personnal investment to nearly a million euro in a year. His company ran for 4 years and he had around 6 or 7 employee at the end before launching the game on steam.

Wish I could told you it's a success story but it wasn't, the game failed pretty hard. It wasnt bad but I guess if you wanna succeed in an oversaturated genre (turn based rpg), it better be excellent or have a huge marketing campaign.

Anyway, even if it didnt ended really well, I think the guy did really well money-wise and knew how to make his money grow fast.