I think that having the kids 50-50 is a good sign, @shitwithsugaron. It makes all the difference that he has them in his own house though. MrSG has his kids just under 50-50 but he’s going to negotiate up to 50-50 with his ex (because he really misses the kids and wants to have them as much as possible).
But a situation like @Sidge describes sounds much less like yes actually in a sensible situation for moving on and dating. Certainly, it’s a big problem is he’s looking for another relationship.
I wouldn’t be happy with a situation where he’s living with his parents (who want him to get back with his wife) because he’s still paying all the bills for his family, and still visiting all the time. Even a plan like @JeSuisPrest suggests (Is he saving whilst he's with parents for a deposit, so you could say in 6 to 12 months time he'll be moved out? Then he'll start divorce proceedings within 12-18 months?) sounds untenable to me really. Because, apart from anything, that kind of vague aspiration is likely to take considerably longer than he might think. I wouldn’t want to be even starting to try to develop a relationship where, realistically, he isn’t even thinking about starting divorce proceedings for another 18 months (and probably not getting divorced for years yet).
Other people may feel differently, but I really just think it’s better to wait until he’s actually got himself sorted and they are living separate lives.
In fact, I think I’d have been less certain about this before my experience with MrSG. When I met him he was separated by (very uncomfortably) house sharing with his ex. It was all totally above board (in fact, she had an affair and was continuing to see the OM). He’d just started divorce proceedings and the house was up for sale. Tbh, he was pretty naive about how long these things take. I was too, but only because I’ve never been married. His ex eventually moved out and the divorce will be final soon (depending on how long the courts take) but the house is difficult to sell.
Obviously, I think MrSG is totally great (and I wouldn’t want not to have met him) but, in hindsight, it would have been a lot easier if he’d had (or currently had for that matter) his life properly sorted and then I met him. Apart from anything, I wouldn’t get weird looks from some of his neighbours when I visit his, because his ex decided to lie and tell them that they split up because he had an affair with me (she didn’t want to tell the truth because it makes her look bad - I’m 100% certain about what actually happened not least because I’ve seen the new relationship announcement on her FB from long before I met MrSG).