Questions about Spanish freelance autonomo visa

Hi everyone,

I am planning to move to Spain in order to work as an autonomo (self-employed). I am a freelance translator with 7 years of experience. Almost all of my clients work with me via UpWork (formerly oDesk).

So I have a few questions that I'd like you to help me answer please:

1. If all of my CURRENT freelance work originates from outside Spain, and I don' have a particular business reason to travel to Spain (other than my love for the country of course!), am I still eligible to obtain an autonomo visa?

2. I heard that having a viable business plan stamped by an organization approved by the Spanish government (such as Unión de Profesionales y Trabajadores Autónomos (UPTA)) is a crucial step towards getting the visa. Since I am outside Spain and can't get UPTA's stamp, is there another way to have my business plan's viability endorsed? Can I get my business plan approved by an organization similar to UPTA in my home country?

3. I read somewhere that once I am in Spain, I'd need to be able to invoice my clients directly and have them deposit funds directly into my bank account without going through Upwork's system. Is that true?

Thanks a lot!