Learn Spanish (Latin America): Yo haría la maestría; sin embargo, es muy cara. - I would do the master's degree; however, it is very expensive.

The verb hacer (to do/make) has an irregular stem in the conditional tense. Instead of using the full infinitive hacer as the base, it changes to har-. Then you add the standard conditional ending -ía for the yo form, giving you haría (I would do).

Is the pronoun Yo mandatory at the beginning of this sentence?

It is not strictly mandatory, but it is very helpful here. In the conditional tense, the yo (I) and the él/ella/usted (he/she/you formal) forms are identical: both are haría. Using Yo avoids any confusion about exactly who would do the master's degree.

What does sin embargo mean, and can I just use pero instead?

Sin embargo is a common linking phrase that translates to 'however' or 'nevertheless'. You could absolutely use pero (but) instead, but sin embargo sounds a bit more formal and is great for connecting two contrasting ideas, just like in English.

Why do we use es instead of está when saying it is very expensive?