This industry is controled by ex-SB; you won't be able just to start your own firm just like that.
Plenty of security companies around that aren't run by ex-SB types. The big ones might be, but the smaller local ones certainly aren't.
I know one guy who used to be in the business - no SB links, but had a habit of beating up drug dealers in his younger days.
Then after a few years, start up by myself
In all honesty - if you have the money to start - then it won't be impossible. You might actually find that there's a demand for a reliable, non-Polish business which provides such services, especially for foreigners who might be loathe to trust Poles. I know that if I was dealing with something like this, I'd prefer to work with a British guy with experience than a Polish company.
The real difficulty will be attracting good clients - but if you target non-Polish clients, then you might just have a niche in the market.