How should I deal with money I found in front of my house, and its owner is unknown? Is it permissible for me to take it if I am in need of it?

This money falls under the ruling of a lost item (Luqatah). If it has value, it is obligatory to announce it for a year. If it is insignificant, it is permissible to take it, and it is not obligatory to announce it. Insignificant money is that which is considered trivial in your country's custom and which people of average means would not bother to pick up.