I am Romanian and Russian. No Latino blood.
Besides HS Spanish and a major in college, here is the bottom line:
6 months of grammar studying. This depends on daily/ hourly per your cognitive skills and study habits.
The rest is vocabulary. You should be able to converse at college level in less than 1 year.
Business papers and executive letter drafts will take more time and will depend on various resources and tolls to ensure that there are no mistakes.
Probably the best self investment for a solid career, less stress when traveling in Spanish speaking countries and the ability to live abroad to the max.
Good luck...