I am a permanent resident in the US. I've been offered a part-time job as an overseas software developer for a very small company in Spain. Their idea is that I'll give them invoices for the software I'd make, working from my home in the US. I don't have experience with taxes beyond being taxed as an employee in the US and my home country (not the US or Spain), and I wonder, is this even feasible and reasonable? I'm trying to find out if all the work setting everything up is worth the trouble.
I'd have to register myself as an independent contractor in the US, first thing. Can I then bill somebody overseas? Do I have to file US and Spain tax returns? (I guess I don't have to file a Spain tax return since I'm not a resident). Is there something else I need to consider?