Depending on the multicade it might be illegal.
it might use MAME, one of those 60 in 1 boards, or be specific for home use (free play only). There are a few that are fine for commercial use, but they are usually limited on the number of games.
That being said, 99% people aren't going to care or even think about it.
There are a bunch of bars with playstations sitting out for patrons to play (technically that is illegal, but no one is going to enforce it)
I think pandoras box is set-up to accept coin, though I've never tried it.
I went the ultracade route since it was technically legal for commercial use and it had the most old-school games on it. Found a bootleg hard drive on ebay for $100 bucks, think it had 280ish old school games on it. The computer is type specific, you can still find them on ebay and KLOV.
For me having a bunch of old-school arcade games doesn't make a lot of sense, based on earning potential and the room they take up. I understand the appeal of the original cabinet and board (no missing frames, original controls, artwork) but...