It's always interesting to see how others approach this challenge, and this is quite similar to mine! :)
I also just completed this scenario, and very similar to yours, I also placed my sim in HoB, which seems to be set up well for this type of gameplay. It was rags to riches (no money, no house, no items), living off-grid/simple living in the park in Bramblewood. Most of her earnings were from foraged plants and collectibles sold from the sales table, or to the vendor, at the start. Then from items she received from Sophie and a few of the critters, she was able to start a profitable garden and a chicken coop. Over time, she was able to move to the 64x64 lot to build her house and farm.
My sim was pretty lucky. She was able to acquire a money tree seed from a sales table and found orchid seeds a number of times from Sophie! With the two money trees, her garden and chickens, she completed the scenario in about two seasons (set to long). I also made sure she sold off her produce at the grocery stall during the fair, where she can make a profit of 25 percent. I also limited her sales table at 25 percent.