I don't think financial incentives will actually do that much, it's generally seen as something that works only marginally. People get more kids when they get stable/good jobs, have a support network, have a culture that incentivizes births.

South Korea is currently throwing money at the problem, upped parental leave even did some things to make it easier to retire if you got a lot of kids. I'm almost certain these things won't meaningfully change the situation (maybe go from 0.8 to 1.0) as all korean children are expected to get good jobs (white collar, certain professions) , they structure their society towards this and it's impossible to get a high birthrate like this.

I actually read about how something like presence of nuns in your town in italy was quite correlated with birthrates as it basically relieved all women but the nurses of some duties. In Korea you can see how the stability leads to a very significant effect on birthrates as Sejong is by far the highest birthrate region. Interesting since those really obsessed about birthrates also seem to hate the worker protections that make it difficult to fire people. I guess housing is another of those stability factors since renting really ups the risks of children.