If you're smart, you won't work for someone else, you'll work for you. Don't wimp out and become someone's full-time employee/slave. You'll wake up one day in 40 years and realize you blew your life on yet another hamster wheel in a different place.
You can probably rent or "borrow" a room or somewhere private for sessions from an existing therapist or in a clinic that is well located on a percentage basis i.e. if you charge 500 pesos for a visit, your host gets 100 of that. OR make house calls and do the sessions in your client's homes - the transport cost getting there will replace the rent for a space.
Find somewhere close to where you will live so you aren't eaten up with transport costs, unless your housing is not a great area. Poor people won't spend 100 pesos on a dentist once a year so they probably wouldn't spend 500 a visit for their issues.
Business cards, a cell phone, and lots of networking that doesn't cost much upfront. Target English speaking foreigners that need help - there are probably enough in Guad to create your own niche and they'll probably feel more comfortable talking in their native language.
You probably won't make a lot in the beginning, but in time you will gain clientele. Leverage your English skills, don't charge too little for your time, and when you're not with a client, be looking for ways to gain other clients instead of wasting that gift of time.
Check with the local hospitals or government agencies that deal with mental health issues. Many medical people take a part time job for 2-4 hours a day to pick up their grocery money and run their own consultorio elsewhere where they make much more. In the beginning of your time here, it would help. Good luck !