I'll just add a bit about my own experience. I think it's a bit different in the U.S. (I'm assuming that's where you're from) in that people do tend to start earlier, whereas the recommendations here are from 6 months. But in my experience, starting on solids actually means you feed them more rather than less, so if your DH is hoping to cut down on some work by starting solids early, I would caution that you'll actually be making more work for yourself sooner. They often don't cut down on milk feeds until they are taking a significant amount of food and calories from solids, which usually happens by about 8-10 months. A little bit of baby rice means you'll be feeding solid meals however many times a day you chose to offer it, plus all your usual milk feeds. In our case, my daughter started to decrease the amounts per feed she had maybe around 8 months, but only dropped a bottle at 9 months (the overnight one) and then dropped a daytime one by 10/11 months. So you're potentially looking at quite a few months of doing both solid meals and bottles until you hit the point when you'll be doing less work. That said, my now 3 year old still eats 3 solid meals a day, plus 2 snacks, plus a cup of milk before bedtime, which works out to be still feeding her 6 times in a 12 hour period. That's about as many feeds as she had during the day at 6 months, just that now I have to prepare or cook them instead of just making a bottle (which frankly is easier!). So I guess the reason I say that is just to caution your DH against thinking that starting on solids makes for less work. It's definitely more and especially up to about a year when they still have lots of milk feeds too.
Beyond that, if you do decide to start earlier, it's baby rice or pureed fruit or veg. I'd just go with the fruit or veg. It's cheaper and you likely make it or eat it every day anyway, so you can just puree up a bit of something you already have to offer instead of buying an expensive pre-made food. But whatever you decide to offer, it should be on a spoon, not in a bottle. It's a very old school thing to put baby rice in bottles to thicken the milk, but it can be a choking hazard, so I'd stick to spoonfeeding if you want to go for it.
As for when they're ready, it should be when they can sit up safely in a high chair without slumping over or backwards, which can be a choking hazard. We did baby-led weaning which is self feeding and finger foods (like normal food like you or I would eat, no purees or mash) and for that, they're ready when they can also bring food to their mouths themselves and have an interest in trying it, which is usually around the latter part of 5 months to 7 months. Hope that helps.
