Not sure what you mean "in startup". Are you referring to a tech startup?
Do you have a job offer already and are you certain they will provide legal employment? The government now makes it much more difficult to stay in the country without legal registration (provided through legal employment).
I don't know what the monthly salaries are for waiters/salespeople, but it's not much. I'd guess $300 on average.
I'd say any time of guy is welcome in Kyiv as long as they are respectful and kind.