We keep Muscovy because they roost, we can't house ours here as our pond is big, so Muscovy for the most part suit us as they keep away from ground level at night when predators are around. They are genetically nearer to a goose and only lay from Feb through to August.
Ducks can't jump up to levels like hens so a flatish entrance to a house is needed. They won't automatically put themselves to bed like hens so you'd have to do it. For that reason they are very likely to be taken unless you do it every night. Sods law if you miss a night that'll be the end of them. They lay at odd times of day so bushes etc nearby are good.
They totally love to dabble, it's their favourite thing. Wet, muddy ground is great, puddly areas fab. We had a 2x1m pond but it proved a hassle, if you do it this way then clean it out say every month but you must must keep a bucket (or two better) of fresh water every day they can drink from and douse themselves with. We have a big pond and river and once you see them swimming on the pond you realise how rubbish a wee bath is. They love swimming.
I use mixed grain or pure maize and put out half an iceberg lettuce each week, bread should ALWAYS be given wet, and must be brown, white will be like glue in their system and will stick in their gut. Worm them every 3 months, a mucky backside, a limping duck, worm them and they are almost always fine in a few days.
Why not try call ducks which are cute (but noisy) or runners are funny. Ratio of a drake to 4 ducks is good. You can sell the eggs and the offspring - people will buy male runners because they look funny but you might find it hard to sell drakes of another breed. As for making money, keep up the day job. It might earn you bob-a-job money and if you're lucky you'll get back what you spend.
Duck antics are great though, they are good fun. Some males can get quite aggressive though. Do your research and think about what type of duck would suit you. And give them space, they are messy. Tell us how you go!