Heh I was asked to write briefly for the HoF interview (I don't think that was much of a success, unfortunately
), so here goes a slightly longer strategy post.
Career CapsEssentially, the approach is to start with Professions, as they reward you with lots of job experience for building skills. I sent Kanye to China on Day 1 to grab the books and ore spawns ("Telescopic Metal" opportunity). Smelt the bars, sell all of them along with the books, and you should have 50,000 for Swimming in Cash. Then get Entrepreneurial Mindset and Fast Learner on one Sim and Motive Mobile on the other.
Once a Profession is done, I would pursue normal rabbit-hole careers utilising the skills built in the profession. You'd want your Sims to have Ambitious, Workaholic and Schmoozer traits to push the Ask for Promotion mechanic as far as possible. By the time Sims start doing actual careers, you'll want them to have Multi-Tasker too. Also, once you quit Level 10 of a job, you can start again at level 5 in the career. Thus, for the double-branched careers like Evil or Film it's best the same Sim does both branches.
In particular, for the Criminal career, you'd want to Work from Home enough so that you can fill the bar even with only 2 or 3 hours of "Work Hard", cause there sometimes are bugs with the career. I'm not sure it was the best decision (I picked it 'cause it's a double-tracked career) - I fell behind schedule when Drifter got arrested!
Finally, there is bound to be down-time while you're pursuing the rabbit-hole careers. (You can only Ask for Promotion once in 3 days). So use this down-time to train up the skills needed for self-employment careers and earn money. Do note that since the credit for selling items depends on when the items were sold, not on when they're made, you can just save up everything, go to City Hall, register for the job, sell, and BAM! Instant Level 10.
Drifter: Firefighter - Pro Sports - Military - Investigator - Thief - Photographer - Angler - Band - Evil - Rock - Symphonic - Inventor (12)
Kanye: Stylist - Ghosthunter - Medical - Forensics - Painter - Business - Spy - Actor - Director - Sculptor - Education (11)
Several people accomplished 24, which I must say is impressive - it's pushing it. (I shouldn't have done Pro Sports...) 25 or even 26 is probably just about barely possible - I should have shot for Gardening, which can be done (I think) by planting 4 money trees in a house then moving out. I didn't do Writing (the whole skill slipped my mind), and I wonder if Daycare is possible to clear efficiently. I assumed Architecture was illegal (counts as modifying the houses).
New DigsThis challenge MUST be played in Union Cove to maximise the score from moving. Otherwise, there simply aren't enough premade high-value lots to get a big score; Bridgeport and Sunset Valley have potential house value totals around 5-ish million, but Union Cove's potential house value total for 23 careers would be close to 11 million, I think.
As part of my research, I emptied the town and took note of the values of the lots. This should give you an idea of which houses you should try to incorporate into your plan.
Now, you'll also need to somehow remove the Sims already living in the houses. You can't use Edit Town to evict them, so... you'll have to do things the dirty way i.e. starve them. You can't use Build Mode to put them in a room, but there wasn't anything in the rules against locking doors - so you can still lock them in the house. Be careful doing this though - one of the Sims in the town (Moira Dernier O'Carter, if I remember correctly) has the Loser trait, so you cannot kill her in this way. Leave the Modern-O'Co and Affiliates household as it is.
As for the items, focus on using them to buff the value of the house as close as possible to the next house (without going over or equalling it). Items bought depreciate to 85% of their value when the value of the lot is calculated, so bear this in mind when buying the items to close the gap. (if the difference is say 1,000, you'd want to divide it by 0.85 to get an estimate of the value of the items you'll need to buy - in this case 1176.) I managed to score a few "direct hits" with houses being worth exactly one less than the next house.
You'll need a lot of money for the moves, but should be pulling in a lot from your career topping especially with the self-employment careers. However, when moving to the final house I made sure I had at least 2 million Simoleons, as the best thing to do to jack up the value of the last lot is to buy four Leon's Fountain of Youths (495,000 each, total value 1,980,000). Also, to avoid depreciation, only move in on the final day. (It's quite a risky move, I admit. If Story Progression moves in a household on the final day, you're stuck.)
To rake in the Simoleons as rapidly as possible, I trained Drifter up in the guitar exploit (to about 2500, I think) during his holidays to China. Thus he blasted through the Band career and had several millions in tips by week 12. Also, note that taking two Sims together with Prepared Traveller grants a total of +6 days to both Sims on the trip, giving me even more time to "play" guitar.
I'd believe an optimal score is around 11.5 million and 26 careers or 41,400,000.