Grandparents' rights vary from state to state. Most of the time, grandparents' rights come into play when the parents won't permit the grandparents to have contact with the grandchildren. That doesn't sound like your situation. It sounds like you're wondering if your grandchild is being adequately cared for, and that's based on your observation. You should proceed carefully. Do you have proof other than hearsay that the parents are doing drugs? What proof do you have that the grandson is not receiving adequate care? In most states, they're going to be reluctant to remove the grandson from the parents' custody. If you can demonstrate with some reasonable certainty that the grandson is being harmed, then by all means take measures to protect him. On the other hand, doing it on a hunch might involve you in a bigger family squabble, with less access to the grandson.
Pro bono work is seldom if ever offered in transactional law where damages are purely monetary. Cases like that are very time consuming in the first place. Secondly, attorneys who give their time in this way are usually advocating Constitutional claims, childrens' rights or the like where there is some pressing public policy issue at stake.
If the agent/owner/broker did not complete the TIL properly and there is actionable fraud, the first thing you could do is report this to the Department of Real Estate (or whoever regulates agents in your state.) TIL violations, if they are material, often result in recission of the transaction and/or sanctions against the person who violated the law. If you could be more specific about your claim, I might be able to suggest something more specific for you.
While there are probably few lawyers who would take this case on a pro bono basis, there are many who have expertise in this area. Poke around the yellow pages and try to get some recommendations from people in your area. If there are material violations, you will more than likely prevail. But if the irregularities are not serious, you might not. Again, let us know what happened and maybe I can make better suggestions.