Moving your sims in an existing household and bulldozing their lot would give you up to 260,000$ for probably two minutes of loading and playing in menus. Than if DLC are ok, I would do Max lvl painting plus create a club of sims that paint because you can sell their painting. All you need is a ton of easel

An other idea would be to have a big family and to mass produce gardening product. Here again you can have a club to help, but in that case the other sims would also harvest your plant so you would have to be careful to harvest everything before you start a gathering.