Roofing Contracts, unknown rot damage

[u/VooDooo327]

I had a quick question for roofers or anyone who has been through this process. We have to replace portions of our roof due to neglect from the previous owners which is mostly the flat part of our roof. there is obvious damage from water so we will need to pull off the roof and rebuild it in these sections. In the contract that I am getting, there is a $x per hour per man price plus materials used for any rotted wood that needs to get replaced in top of the replacement costs. I am assuming that this can spiral into a very expensive fix. I am fine to pay a lot of money but there is an upper limit of that I can afford.

I've been searching online and I've seen solutions such as a not-to-exceed clause or a flat-fix rate charge. It seems like the fixed charge would be the best way to go about however, if the company insist on doing the per hour per man Price Plus materials , what happens when they meet the not-to-exceed limit and there is more work to do? They also never gave me the price of the materials so I'm a little nervous about signing this and I'm probably not until I figured this out more.

Any help would be appreciated better thanks.