1) It's helpful when you provide which country the testing is performed in, as the laws are not the same in the entire world. Some countries has very strict laws on hacking, where you can barely own a hacking tool, others prevent creation of viruses (even if they're not used), and some has very strict rules of eavesdropping / man in the middle attacks.

2) If he really owns this home network you want to hack remotely, the owner of the network and devices connected to it, must sign a real contract specifying various topics such as scope, liability, and so forth.

3) In some countries you may need to warn your ISP. Otherwise they may throttle, block or report your malicious traffic.

Final words: There's no easy way to obtain a get out of jail card, you need to have proper permission from the owner of the target network, and preferably also have permission from the ISP, and also check which countries or perhaps states your traffic passes through, because if your traffic passes through USA and you're based in e.g., UK, Germany, Spain, or whatever, then as soon as the traffic enters USA, it's under US-jurisdiction.

So, it's not just like "that", you have to be careful and do it right.


Conclusion:
You will probably learn more by installing Metasploitable in a VM on your own network and attack that, at least for starters. There's various Live CD OS's that you can sharpen your pen test skills with.

A site for a great overview of diffrent vulnerable systems/apps for a pentest lab is:
http://g0tmi1k.blogspot.com/2011/03/vulnerable-by-design.html