Let's say 500€ daily rate (which is probably average in France with a very large standard deviation between Paris and deserted zones and factoring varying daily rates which are domain specific and experience related. No way a junior RoR freelance would make 500€ in Massif Central for instance. Likewise, 500 is low for an experienced data science freelance working in banking in Paris). 206500=60k€ gross

After social contributions, 30k€ net revenue in France (actually a little more but I take the liberty to round that down).

In large cities, 33% of revenue for housing is not uncommon. We're left with 20k€, of which we have to substract revenue taxes (rule of thumb in that revenue range, about 1 month revenue per year) so here 5k€. 15k€ for 6 months. living frugally you can probably save 2/3 so you can save 10k€ in 6 months.

Assuming these ratio, it would take 2.5 years of steady, near fulltime employment as a contractor to save these 50k and go all out on your project.

1. Assuming you keep it in a company, and actually are smart about releasing it when you need it, so you don't have to pay all the tax upfront.

"keep it in a company" at least in France won't really help you, as social contributions are collected every 3 months.

They are very good at hounding you to pay (and inversely keen on giving you back any overpaid amount ;-) ) so the incorporation does not really help here. You still owe them about half the gross revenue.

Sounds like a good reason not to bootstrap a company in France!