Start with a Behringer, no doubt about it. If you're still in the "I'm not sure if I'll stick with this" phase, throwing 150 euros at it is already a risk, let alone 400-500. The important thing is that you start understanding the workflow: how you connect MIDI to your DAW, how to map controls, how to build a track. A cheap keyboard works great for that.
What really matters isn't the instrument but the software behind it. If you use a decent DAW with quality VST synths, the difference between a 100-euro keyboard and a 500-euro one is way less noticeable than you'd think. The key sensitivity on an entry-level Behringer does the job, sure it's not the same as professional models, but for making early house music it's more than enough. You'll hit the real limits when you get more demanding, like if you want to play complex velocity-sensitive stuff or use the keyboard live, but we're nowhere near that yet.
Wait to spend serious money once you've done a couple of productions and have a clearer idea of what you actually need. If after three months you're still going, then yeah, think about upgrading to something better. But right now it's really premature.