As a boat owner and diver I will tell you - I posed these exact same questions about a year ago here. I got 20 "youll put your eye out kid" type of responses, and one PM. That PM was from a VERY experienced diver and boat captain, and its a great thing that he reached out to me, otherwise I would be still stuck on the cattleboats with everyone else, too petrified to dive off my own boat, based on advice from people that probably dont even own a boat! Long story short, we have dove together for over a year now, logged over 300 dives together from 30 feet, to 200 ft. Many with a dead boat. Is it preferable? No, of course not. But being able to PROPERLY dead dive a boat will keep you in the water a lot more often than not. If you just go out and try to do it with no help, and nobody with experience helping you are asking for a disaster. There are a lot of tricks to keep you out of trouble, and lots of things to know. A few things I will add, for anyone diving their own private boat
#1 Hire an attorney to draft a liability waiver - Nobody gets on the boat EVER until they sign it.
#2 Maintain without question the required safety gear on the boat. have more than what is required, it is your skin after all.
#3 Keep a large (at least 20cf) bottle of O2 with a demand valve and a bag mask on board. I would not dive without this on board period.
#4 Keep PLENTY of tools on the boat.
#5 Read Chapmans piloting and seamanship. Well worth the price of admission. Nobody should get behind the wheel of a boat without reading it. I review and reference it constantly.
#6 Take a first responder course, be sure you can provide CPR and other emergency medical attention
#7 Understand how to properly anchor and secure a boat. I saw something in OP's comments that led me to believe he needs to learn to tie a cleat properly for instance.
#8 Carry a Nautilus life line, or some other method of signalling immediate help if there is a problem.
#9 Be prepared for the worst to occur. Reality is that when you dive off a private boat, bad things can happen, just as when you dive off a cattle boat. If you are not prepared to deal with a life saving emergency situation, then dont dive off your boat.
#10 When anchoring, you can never have too much scope. Become REALLY knowledgeable about anchoring BEFORE you do this.
#11 practice underwater navigation and get good at it. One of the primary skills needed to get back to the boat. As someone pointed out, you can always tie a reel off to the anchor.
That should get you started. By no means is this a complete list, but its what came to the top of my head in the two minutes that I took to post this. You should not take my information to heart, rather use it as a rough guide, and a start to thinking in the right frame of mind. Safety of you and your divers should be your #1 concern at all times. There is an awful lot to think about. You may or may not be capable of doing this, and only you can truly know in your heart and mind if you are. Whatever you do, do not do this without someone with lots of experience, otherwise you probably will put your eye out, kid! There is a lot to know. Good luck, and I sure hope you learn to properly dive off your private vessel, as it is a ton of fun. There is nothing like anchoring next to a huge wreck, and having just you and your buddy in the water. Pure, peaceful bliss!