I had a dog until I was about 25 and I found it pretty straightforward. I lived abroad and often where I lived people don't keep their dogs indoors but mine was.
I suppose the hardest part was not being able to leave him alone, I didn't ever leave him alone for more than about 3 hours but to be honest that was the only difficult part, apart from when he had to be put down, that was devastating.
I am now married with 3 DC and we are planning to get another dog but every single person I've mentioned it to (funnily enough none of them dog owners) has told me what incredibly hard work it is... I am a SAHM so will spend most of my time with him and I love long walks. Obviously I am more than happy to put the time in to train him too!