Read the lien waiver carefully [...] they can try to make it mean you can't ever ask them for funds on same property ever again
Excellent advice! Just because it says "lien waiver" on the package doesn't mean you know what's inside. I saw a "non-disclosure agreement" that, instead of the usual "we won't steal your stuff", actually said "you hereby give us all all your stuff." In your case, Cletis, you probably don't want to waive change orders, other claims, future work, the simple right to get paid, etc etc.
Also the rules, and thus the meaning of the waiver, will vary state by state. In New York, these
apparently are enforceable only upon or after payment, as opposed to (say) before work has begun.
Ditto in other states, and for federal projects, according to
this essay, written for the contractor (rather than the payor!) which gives a few warnings. (For example, to avoid giving acknowledgement of payment without conditioning the waiver on a stated dollar amount.)
http://www.dysarttaylor.com/news-events/blog/lien-waivers
You don't want to waive lien rights on future work. Nor do you want to give a
final waiver, against the full amount due, in exchange for a
partial payment.
It might be worth having a lawyer look at this, especially since it's "a really big job." In the worst case, a friend who's used to looking at contracts might catch something, but you would rather have someone who knows Ohio commerce law.
For a randomly-googled-up example of a relevant Ohio-specific law,
apparently
Those who bill and receive payment, and fail to pay their subs and suppliers within ten (10) days of receipt of the money for that work, face the sizeable risk of being liable for 18% interest and legal fees under Ohio’s Prompt Payment Act.
These lawyers caution that you'd want to understand how to use that Act, especially if there are disputes:
http://www.taftlaw.com/news/publications/detail/1204-ohio-s-prompt-payment-act-revisited (Caution: especially-lawyerly prose.)
As with any contractual request, you want to ask, and understand, what's motivating the other guy. (This is why I never want to involve lawyers until AFTER there's a handshake.) For example, you shouldn't need to give protections to the owner that are already granted by state law: the Ohio AG tells homeowners that according to
The Ohio Mechanic’s Lien Law[...], if you pay the original contractor in full before receiving official notice of a mechanic’s lien, a lien can’t be placed on your home[....]
The should-be-obvious disclaimers: IANAL, YMMV, park and lock it not responsible. Emphasis added. I've wrangled contracts, but nothing lien-related, and very-much IANAL. Also: you might find the various links helpful, but I can't vouch for any of the sources. (Except maybe OhioAttorneyGeneral.gov, I guess.)