Rooms

Actually you might do better building a basement and putting a nectar rack in there, getting nectar cheap from the consignment store and letting it sit in the basement to increase it's quality over time (I don't know how much profit you would make from this I've never tried it). Nectar also ages by the week so you'd have to play a bit before you could use this. You can also set up some expensive fencing around your yard and change it to cheaper when you need some quick simoleans later.

There's also a great money making item that's dlc from the sims3 store (the grandma's canning station) where if you put three fruits or veggies in you get three jars of jam worth 100 simoleans each which is great for early money making.