I don't think anyone would want to hack your site for that misery $500 you offer as bounty when they can afford to wait for the site to be loaded with more funds and then break into it and steal all. My suggestion would be that you get a high fortification for your site, not looking for someone to try hacking it.
Exactly! Moreover,making it open to public that the website may have vulnerabilities and revealing the project's name would interest any Black-Hat hacker to take advantage of the same.
That is why they are called "white-hat hackers", because they do such exercises as penetration testing for money.
The people could steal the funds anyway if they find a bug, so i do not see a difference offering a bounty for it.
Although i suggest to hire someone personal on such things, like a seperate security expert, whose identity OP knows.
500$ isn't alot, but the point is to avoid any funds getting stolen, so users do not get scammed at all.
Op should hire a bitcoin security expert since most of the back-end flaws exist on the transactions side where most of the money is.Being a white hat hacker myself,let me tell you $500 doesn't mean shit for the Black-Hat hackers.If they want to,they'll hack the website without seeking any bounty in it.
