The New York area does support three teams in hockey - Islanders, Rangers, and Devils - so the notion isn’t out of the question. There are differences, but not insupportable ones - hockey needs fewer bodies to attend, but it starts with a smaller fan base.
Money, as noted, is the issue. The roster is the smallest piece, though at a couple of hundred mil in long-term contracts, that’s hardly trivial. You’d need a third stadium - hundreds of millions, possibly a billion or more dollars. Most of all, you’d need tv revenue and advertising to support that, and that would be almost impossible to obtain in sufficient quantity after the Yankees and Mets have sucked away the dollars.
Note that the other areas with two teams - Los Angeles, Chicago, and San Francisco - are the second, third and fifth largest population and television markets. And only Chicago has the stadiums physically near one another.
That indicates to me that the only other area capable of supporting two teams is Washington/Baltimore, which combined is the 4th largest in population and television. Angelos has blocked a team in Washington, but it’s feasible. It’s also a technicality, since most people don’t consider that one single area. They’re separate television and newspaper markets, after all.
St. Louis had a second team until the 1950s, and the Browns were the joke of baseball for decades. And St. Louis used to be one of the ten largest areas of the country. Today it’s only 18th population and 22nd in television, totally out of the running.
Philadelphia and Boston also lost their second teams back in the 50s, and are still top ten cities. I don’t think either of those areas could support a second team just because of the money and advertising issues.
In these terms, Sacramento, Portland, and Orlando are the top baseballless markets in size. I could see Montreal moving to one of them before either Mexico City or Puerto Rico just because of logistics and ratings, but who knows the way the Lords of baseball think?