I don't want to be the sole voice of gloom here, but I had 2 dogs, 4 years apart in age. Dog 2 never really took to house-training at all! (she's a beagle, to be fair) and oldboy went in a sulk when she came, although evetually seemed to accept her presence.
The walking was fine, although if both were on the lead (as they were a fair bit!) it could be awkward picking up etc.
Fast forward 12 years, and they seemed to be ok, learned to live together, but in some ways they each hampered the other's life, if I'm honest. Dog 1 loved his big comfy bed, but dog 2 ate it. Then its replacement. So they ended up with a plastic bed 
Dog 1 got old and incontinent eventually, and dog 2 seemed to get less tolerant of him.
I sadly put dog 1 to sleep a week ago (aged 16.5), and dog 2 seems to never have been happier We have decided to let her be an only dog until the end now.
Having said that, I know lots of 2 dog families when the dogs are the best of friends, so my story is probably an abberation. But I think it does very much depend on the personalities of the individual dogs, and you don't know that until they are together. I thought old boy would love a canine companion, as he always loved other dogs (too much!) when out walking, but he didn't seem to keen on having witchy-dog there constantly. I thought an older dog would help witchy-dog settle in, but they seemed to vie for attention, and she actually seemed less secure. Now, looking back, I feel like I forced them into a kind of arranged-marriage situation!
But that doesn't mean it won't work for YOU, OP. Just that it's not always as straightforward as you might think. As I said, lots of success stories, so chances are it will be great. I miss having 2 dogs. I keep saying "the dogs" and having to correct myself.