I find you can just push through unhealthiness. IE, ignore it. For example, assume your Health is about 8. You're managing your growth to always have two extra food. When you reach 9, that extra worker starts working on a cottaged grasslands. You now grow half as fast, but are getting the commerce from the grasslands. When you reach 10 pop (slowly!), you stop growing altogether, but you're getting commerce from two extra cottages. Assuming grasslands.
Flood plains are great for ignoring health. They produce three food without thought, which translates to two food to support the worker on it, then one more food to pay the unhealth cost that that pop unit brings to the city. Farm two of them and you can support the unhealth that 5 floodplains gives you just for being floodplains. That leaves the other three to be cottaged. That's -7 food from unhealth before you really feel it, but the benefit of 3 cottages you didn't have before. Or, since these are floodplains, watermills. Then if you have some grasslands or farmed plains... two *more* squares, -9 unhealth food penalty, before you actually *stop growing*. Flood plains rock.
Unhealth limits you, yes, but it limits you quietly... there's no reason to "avoid growth" just because you're unhealthy. (Plenty of reason to add more health bonuses... like granary, harbor, or grocer... which you're likely to want to build anyways.... but no reason to avoid it.)
