In my opinion if they signed a lease and gave deposit to hold the property and it is clear in writing what the next steps are and they do not perform per the agreement then they have violated the contract and forfeit the security deposit because that is what was holding the property and you could have leased it to someone else so technically you could be out potential money.Now the flipside to this is you may be right all day long, but if they sue you over this you have to get legal counsel to defend yourself and deal with the headache and mental strain of battling this, probably spending way more then if you just gave them back the money and moved on.

Unfortunately Coaching soccer was not very lucrative and strained me from a capital standpoint especially when I went into the wholesaling business. 

Does the house have double pane windows?

The main fuse/breaker panel has probably been replaced since the house was built, but don't assume that the wiring has been replaced just because the panel is new. 

I never understood this, I do everything I can to stay away from dealing with family because I love them and don't want to strain relationships over money!

That being said things seem to be working out as most of my costs are geared towards the strain of not having any processes in place.

However, the move and extenuating circumstances have/will put a strain on his liquidity.

Also means vacancy will put a higher strain on you financially since mortgage payments will be higher. 

Sure a 60 amp panel is small by today's standards but do you really need to spend $25K to address it?

It might be worth paying a professional to lessen the strain on your friendship in the event they don't hold up their end.Good luck!