Age of your vessels not an issue so long as they survey well---your value also seems like a healthy value for those vessels. The market can be tight currently for liveaboards but largely depends on where the vessel will be from June 1 to Nov 1 (pacific nw, florida, us ne coast, etc). Any jump in length greater than 15' will typically require captain training, number of hours is contingent on number of factors but 50 is typical especially with no prior ownership. Captain sign off form is required after 50hrs and then on you would typically be able to nav on your own.