Uh, yeah, no.
For starters, you need to write a business plan, yes, it is a business, it might be a non profit business but it has to pay for itself.
At this time you are standing on a street corner saying "give me 500k and I'll do... stuff, promise".
How did you calculate the 500k you say you need, where is the costs breakdown, what is your budget, where is the list of exactly what equipment you will need, how many people will you require on staff, what will be the compliance and legal costs etc etc etc.
Good things start from an idea, but "build makerspace, eh, 500k should cover it" isn't an idea ready to take to market.