Well, I have had the Sims 3 for mobile for about 2 weeks now and I haven't found any "cheats" but I have found my way around this tiny little sim world.
First, thing that is very important is selling what isn't needed right away. I sold my table and chairs ( they will eat standing), the extra cabinet and the tv. To sell the items in the home hit the select button in the far left corner, then go to building mode. After this is done head to the Hobby shop ( you can hit the select button or just walk out the front door and click on the floating city icon). Purchase a fishing kit at first from the Hobby shop. Fish until your thumbs are locked, lol. Then sell the fish at the Quickmart
Catfish sell for 25
Snapper sell for 45
Trout sell for 50
Plus residents like Anya (catfish for 200), Johnny, and Nina will pay top dollar for fish.
You will need a cleaning kit and repair kit - but the first thing I did for 3 sim days was wake up and fish.
My first purchase was a stove, then the house upgrade (which is offered by notice and you can use your telephone in the sim living room to get it for 1000).
Career advancement info
First you can make more money just fishing than at any career I have found as of yet. But you need to advance to unlock more stuff.
So for the science career befriend Anya and have your gardening and fishing skills up) I did this all before I went for the job and ask for a raise until I got up to 260 daily - dont know how to get to the last raise/promotion as of yet.
For the political you need to be at the top of all your skills, befriend all the sim neighbors and be best friends with Ruth.
For the Quickmart you have to befriend Bernie ( which is a bit of a handful he is quick and doesnt like to chat) then you get a raise every 10 days ( with the others I have gone to the final levels all in one conversation). This one is the longest in the career as far as being promoted: the others I have completed in one day with my skill levels up the way the needed to be. Plus in this career you needed your repair skills and cleaning skills honed.
Okay this is a pretty easy thing. Just chat or talk about a skill until you are befriended. Then if you are interested in the sims start with a simple flirt and the bar will show good friend and the date bar. If you just keep up casual conversation and friendly interactions then you will become best friends however, if you flirt, tell flirty jokes, embrace and kiss soon you will be dating. Continue with flirting, kissing and the infamous woohoo sessions and you can become partners. Keep the loving feeling up and you can ask the sim to marry you, which leads to an engagement and then you can pop the big question.
FYI- asking to marry at the other sims house will enable you to use there high end furniture (stove, computer) (Luke, single has a great place to learn to cook) while you save and buy what you need - then just go home invite them over and they will move in. Unlike the other sims games you can only control the sim you originally create and therefore have no combined sim dollars with marriage.
Additionally, you can get money by slapping and kicking over other garbage cans for other sim per request and since they seem to forgive easily you can make up my apologizing for your bad behavior.