As someone else mentioned, there is your red flag. If a company can't put up a good face for the interview and compensate your for your time to travel there, that is a good sign they'll be stingy with bonuses, benefits or other things in the future.
I was impressed by one company I interviewed with, there were prepared to pay me for gas for visiting them because I drove there. Other company which flew me over, gave me an extra $50 for the cab on the way back and for getting a dinner at the airport when I flew back. It is a small, relatively cheap token of appreciation that makes a good first impression.
My advice is don't ask explicitly as the first thing about it, but as they invite you, when picking a time, ask the person making arrangements, what company will compensate you for amongst other questions. This should probably not be the deciding factor and if you really like the company otherwise, still go, but it is just another heuristic to use.
Other red flag -- they give a very small decision window. They don't want you to have time to get more offers in and compare. In that case, ask to midify the date to think longer. That is a good test how agreeable they are. If they don't want to, that is another red flag.