I don't have kids, but I've dated a few people with kids and my ex-husband had a child. From that perspective, my question is always are you willing to be a step parent? If yes, go for it. If not, stay away. Even if you think it'll be something casual, there's always the possibility feelings will develop beyond that, and having to break up with someone you really love because you don't want to be a parent sucks a lot more than just saying no on the first place.

The other thing to consider is whether the other parent is still around. My ex's first wife suuuucked. They co-parented relatively well considering how their marriage ended, but she was also a hypocritical bigot (born-again christian, shocker), which caused some friction when my stepkid was being taught things like, "we hate this person because they're gay." But like it or not, she was going to be around, so I had to account for that in my decision to get serious with him.