There might be some privacy issue with it. A sophisticated actor might able to correlate the traffic of a hidden service (e.g. your lightning node's onion address) to that of the tor relay, which could expose your lightning node's IP address.

You might also try to find out what your ISPs policy is regarding tor relays and exit nodes. Some might threaten you with shutting down your service. If you surf the web from the same IP address, you might find yourself quickly blocked from a lot of services, and you'll need a personal VPN to make the internet usable for yourself again.

Maybe start with a Tor relay first. Running an exit node is a bit riskier depending on your ISPs policies and local regulation.

Source: I ran a Tor relay from home for years