Two Different Domains & Domain Controllers on Single Network

The two domains will not interfere with each other on the same network. There will be no trust established between them unless you manually establish one.

The DHCP issue is a valid point, and your potential fix is correct - You can hand out the DNS address of one domain via DHCP, and use a forwarder to resolve the other domain's namespace. An alternative fix would be to manually configure networking for the clients on one of the domains, and point their DNS manually at the correct domain controller. You can leave the other domain's client working from DHCP.

We have a few subnets that are used for internal testing and have 5+ different domains running on them, no real issues to speak of.

I had a fairly long answer all typed up on why you shouldn't go down this road, and then I reread your question and saw the part where you said that this is in your house, so here's my revised answer:

Assign only one domain's DNS servers via DHCP. On those DNS servers either set up conditional forwarders for the other domain or create a stub zone for the other domain.

I haven't done this so I'm not 100% positive that it would work, but I can't think of any reason it wouldn't.

I just finished doing this for a migration scenario. It worked...Kinda.

The caveat to watch out for the is domain name suffix. If you specify one the clients will have a difficult time resolving some hostnames. So don't specify one. That way, the clients will resolve hostnames based upon the domain they're joined to.

Aside from that, just setup your DNS conditional forwarders correctly and you should be fine.