I've been doing an 8-person household in Sims 3 and then this morning in Sims 4 for comparison.
8 people in Sims 3 get $30,500 to begin with; in TS4 it's $34,000.
A 50x50 lot in TS3 is $5000; in TS4, a 40x30 lot (the largest empty lot I could find; it was in Oasis Springs) is $5500.
I used blueprints in TS3; the cheapest bathroom, 2nd cheapest kitchen, and 3 of the 2nd cheapest bedrooms came to $19,268.
In TS4, I used 2 of the cheapest bathroom, the 2nd cheapest kitchen, 2 of the 2nd cheapest bedrooms, 2 of the cheapest bedrooms, and the cheapest living room and put together a house that cost $25,136.
I still haven't put a roof on. When I tried, I screwed up the interior of the house somehow. I don't know if that's a glitch or my ineptitude. I'm getting used to the camera; the most annoying thing is that you can't edge-scroll at the bottom of the screen. Putting siding on the outside is a mixed bag. You can have it automatically finish off the corners, but holding down the shift button only covers the exterior of a room rather than the whole house.
Being able to put a foundation underneath is wonderful; so is being able to move the whole house. I think I'll like being able to rotate objects by using the . and , once I get used to doing that; it works much better than what I used in TS3. (Now if I can just figure out the roof...)
I've put each of my sims in each of the 8 career tracks. They pick up skills very quickly, mainly because you're notified of that as soon as they start working on one. In my TS3 game, it took me until 5:30 pm to get everyone employed (the self-employed painter and writer had to get their skill points). In TS4, everyone was employed by noon. In TS3, I gave them a computer, an easel, a chess set, a treadmill and a gnubb set. In TS4, they have a computer, an easel, a chess set, a punching bag, and an observatory.
Sims get focused by using the observatory. My painter sim has the perfectionist trait, and he got embarrassed by how awful his first painting was (it was only okay) and had to go hide under the covers. I gave him a pep talk at the mirror, though, and he's fine now. It costs money now to paint -- $50 for a small, $75 for a medium, and $100 for a large. On the other hand, my sim's first painting sold for $74, for a profit of $24.
I really like the look of the game, and I'm going to enjoy playing with emotions. Are they smarter? Apparently they don't react to fights or deaths in their vicinity, and someone reported that a woman walked in on her cheating husband without reacting either. On the other hand, last night when my sim started a conversation with a woman in the museum's bathroom and several other people walked in as well, making it quite crowded, my sim and the person she was talking to exited on their own. There might have been some clipping; I didn't notice because I was so surprised.