As part of an sales offer, i was asked to sign a document that says that i am waiving the opportunity to conduct a risk assessment or inspection for presence of lead-based paint hazards in the housing. Based on the seller disclosure, he is not aware of the presence of lead-based paint, however he has never done a test. I am not feeling very comfortable agreeing to this, because i will ultimately be liable in case lead-based paint will be discovered at some point down the road. Any thoughts or advice?

I would be concerned as well.  I don't know what the remedial actions required should there be found that lead-based paint is in the home.  Most likely it is being built the 1900s.  The reason the seller doesn't want you to do an inspection is that if you do one and find evidence of lead-based paint and you decide not to buy the property then they will be required to disclose that information to future buyers.   I would go under the assumption you have lead-based paint and find out what would be required of a seller to remedy the lead base issue.  Also buying a property that old, I would also want to know what the plumbing lines are made of.  Have they been replaced, older homes the pipes were made out of cast iron and many have rusted out.  Have the electrical wiring been redone?  Be careful if your going to use this as a rental and don't know the condition of the plumbing, paint, and electrical.  Cheers

There probably is lead in the original several layers of paint! As long as you're not chipping away at it and then breathing that in or eating the chips you're fine. The thing is that it's covered in several more layers of paint. Even accessing the lead-based paint is likely a challenge. This waiver is typical for every house built before 1978. Nothing unusual here!

Given the age you're more likely to have aresnic under the lead paint, which is covered by newer paint. But as @Kiera Underwood mentioned, it is encapsulated and it's fine if you don't disturb it. Asbestos is similar with the exception of friable materials, like insulation that can turn to powder when disturbed.

As Keira mentioned, all houses built before 1978 have lead paint, unless all the walls, ceiling, doors, trim and everything that's painted have been replaced, or sanded down to bare wood and repainted.  My own house was built in 1973, so it has lead too.  I am not concerned.  

Thank you all for your insights. This feedback is consistent with what I have heard from other investors.

@Bastian Kneuse I know it's been ten months now, but I'm going through this currently. Did you ever end up having an inspection? Did you use the assumption of lead paint in your negotiations? Did either you or seller mitigate this in any way? Thanks!

This has never been an issue. I just went with it. It seems that nobody really cares about it or goes through the trouble of an inspection. Its somewhat of a risk, but very very minor based on what other investors shared. 
Originally posted by @Alexandra Garced :

@Bastian Kneuse I know it's been ten months now, but I'm going through this currently. Did you ever end up having an inspection? Did you use the assumption of lead paint in your negotiations? Did either you or seller mitigate this in any way? Thanks!