Hi LazyCrazyDream,
Have you tried getting a loan from Fujimoto and/or the bank? I have played through the initial stages of the game three times, and all I can say is that not going negative without the help of a loan is extremely hard, if not impossible. If you've already done that and are still having trouble staying afloat financially, take a look at the quick guide below, by user 'igorkeefe':
"Start out with two regular offices, your own office and a break room. Hire five idols and two sales people with deal skill. Research photoshoot -> set the salespeople to auto business proposal and make bucks -> get third office for production-focused employee and let them research when they aren't doing anything. At some point, start an internet show with all member cast for fame and that promotion requirement. Whenever you can, do promotion to steadily build your fanbase. Advertisement deals are good too bút watch the stamina.
Once you got decent fame, get a huge loan of 8.000.000 - 10.000.000 Yen from the landowner and pay off over six months.
Use the money to build a dance room and a recording studio and hire production focused people there. Start producing singles and release them each month whenever the button is green. Digital release is very good for at least the first seven or so singles because there's no production cost. You will lose money but the loan tides you over and eventually you make more and more profit until you are financially comfortable. Try to level your promo and performance for short-term money and lots of fans (more fans = more singles sales). I think the 720 fans promotion level is easily achievable and makes a large difference."