Highly. I have a few male friends (one is 25) and he already bought his own house (because he has a permanent contract from his work) and then I have another friend who is 29 and he also bought his own house. I think it is impressive and it shows commitment (and dedication to some extent).
It shows he is a person who is willing to commit to something (very long term) and settle down. He wants things out of life (and is going after them). This is for someone in the range of 25-35.
While it would very much impress me and give me a positive view of him to have his own house, this is just a plus bonus... It is in no way a prerequisite whether we date or not.
Honestly, it would impress me, because I am still young. Having your own house means you've made accomplishments in life and can also represent having a good work ethic and being responsible, which I'm attracted to.