This is Ellatrue's original Sims 2 Poverty Challenge converted for Sims 3. Credits linked below.

INSTRUCTIONS:

Create a teen Sim to be the founder of your impoverished family. Move the sim onto a vacant lot and set family funds to $100. Survive and thrive as best you can. The challenge ends when the youngest grandchild of your founder dies of old age.

POINT SYSTEM:

+35000 if your sims do not marry/move in anyone, ever
+1 for each simolean of the family net worth
+3,000 for each child raised to teen
-5,000 for each child taken by the social worker
-3,000 for each accidental death
-1,000 for each promotion

RULES:

1. NO FIELD TRIPS
2. NO PRIVATE SCHOOL
3. NO AFTER SCHOOL ACTIVITIES
4. Your founder Sim may only ever work in a teen career.
5. Other sims MUST START AT THE BOTTOM of the career ladder in any career they choose. You will lose points with each promotion, so think carefully about your strategy, and whether you want them to be promoted or not.
6. All children must have the swimming in cash or living in the lap of luxury LTW. Grandkids can be anything.
7. NO ADOPTION- you are poor, remember?
8. NO REWARD OBJECTS
9. Only NPCs or service sims may join the family. Nightlife users may not ask them how much money they have.
10. Sims may only visit their own workplace, school, or small park - everywhere else is way too expensive!
11. Hacks and custom content are allowed, but not if they are against the spirit of the challenge.
12. The poverty challenge stays on the poverty lot- if a sim moves out, they are no longer considered part of the challenge.
13. Teens may move out with an adult, but not alone. Kids and younger may not be moved out, period. Otherwise you will lose the 3,000 child points from raising them.
14. Sims may not become a buisness partner or own a business or venue.
15. All seasons must be a minimum of 8 days long.
16. Lunar cycle must be set to all phases and the cycle must be a minimum of 8 days long.
17. Lifespan must be set to between 70-100 days.

Credit where it's due: https://modthesims.info/showthread.php?t=335023

How about other means of making money aka, painting or gardening or other skill functions that they can sell the created product?