Unless your rabbit can be neutered, you can’t bring another rabbit into the house to bond with him, even if that rabbit is spayed or neutered. Six years old is older than normal for neuter surgery, but if a vet has run blood tests to check for organ function and given him a good checkup and is confident that he is okay for surgery, you could consider it. You do need to know that while most rabbits love having another rabbit companion, there are some rabbits who prefer to be the sole rabbit in the house, and will never get along with another rabbit. That is rare, but it happens. In that case, you would have to permanently house them separately, and let them out separately for play and exercise. Not everyone has room to do that, or the desire to have two rabbit areas to maintain and two schedules to follow.
Most rabbits sleep for a good bit of the day, so if you are able to be with him in the early mornings and late afternoons and evenings, your rabbit may be fine with that.
It’s impossible to know how your rabbit would react to another rabbit. He may absolutely fall in love and be very happy with another rabbit, or another rabbit could bring upset to the house. In any case, you definitely would need to have him neutered first, and allow a month or so for the hormones to die down before getting another rabbit. You will have to go through proper bonding procedures if you do get another rabbit. There is a good article about bonding here, under the BUNNY INFO tab at the top of the page, and here is another good article. http://rabbit.org/faq-bonding-multiple-rabbits/. Plus, you can always ask questions and get help here in the forums.