I'm thinking officially no longer than 3 minutes. (But, like, if it runs to like 3:07, no biggie). No overly-loud bullshit. Try to work brass in there somewhere, can be either "orchestral" or synthetic. Usage of samplings is allowed, but try to figure out notes yourself if you can. That being said, Mixcraft (unless this has changed recently) has a free trial where you can "mix down" your work for up to 30 days. 👀