Laid off from job in a very niche industry, want to do consulting for competitor of former employer.

I got laid off from my corporate strategy job in a very niche industry. Without going into specifics, it's so niche that my former employer essentially has a monopoly on the whole industry, but there are a few competitors entering into the arena now.

To make lemonade from these lemons, I was thinking about approaching these competitors to see if they wanted me to make them a financial model or give them some advisory over it. As I'm basically one of a few people in the world that has underwritten these specific types of investments and have seen how they actually play out in real life, I think I have a lot to leverage.

My question for you guys is, is there anything I should be wary about when doing this to protect myself legally? I never signed a non-compete clause with my old company. Can I talk about the actual performance of my old employer's investments? Or would that be against the law? Also, how much could I charge them to build them a new model?