I also suggest keeping a large amount of money back for Real Estate. Now at Generation 4 I have earned back all the money I have spent on Real Estate.
If you have a Dynasty in Twinbrook and don't mind moving in several people, DeAndre Wolfe has a Car worth $105,000 and briings in $20,000. Then move in another rich Sim and you could get another $50,000.
Twinbrook is good, but Bridgeport is better.
You have Lola Belle and Matthew Hamming (who are mighty rich and the latter is rather handsome). I also recommend moving in the "Bridgeport Hagness", Olive Kipling and maybe partners for the ladies -- Jack Porter (maxed out Mixology (oh well), level 5 Cooking, two need bars are permanently frozen) and Like Reddy (level 5 Painting, maxed out Mixology/Gardening) are good choices.
As a matter of fact, I'm using this exact plan in my official dynasty, except I move in Michael Sleep instead of Olive Kipling, as a spouse for Lola and the father of the second generation. I realize that when the second generation is born there will already be 8 Sims in the house, but since Matthew and Lola are Adults (I believe Lola is halfway through it already), and I'm going to make all my Sims wait till they are nearing their Adult birthday to try for baby, I don't have much to worry about. Oh, and Michael, Jack, Liko and Olive are all homeless townies, so it's still a question whether they'll be in the Dynasty household or not, as there is a sheer possibility of them becoming vampires.