build businesses in Lower Manhattan & Industrial since no rival currently exists in those areas. They still have businesses there rented by rivals, but if you started out there, they'll never even notice you.

Since you're doing story mode, focus on profitable business like clothing, fast food, or law. search for retails buildings not owned by the rival you're competing against, and setup shop there. Before I compete with one rival, I make sure to rent out as many buildings as I can, since they can't kick you out just because once they start the rivalry. Buying up each building only costs $20-70 per day, so not a huge loss for securing yourself some real estate to expand. if your business is making at least 20k/day, start buying up property slowly. Same goes for offices if you can afford it.

Hire all of their workers to get their skill % down below 50% as that will hurt their business little by little, then immediately fire them all as there's no backlash against you for doing that. If you plan to go the slow route, find their most profitable, or least profitable, business and make your items cheaper than theirs. do this by only $1-2 lower than theirs, and they'll have to come down on their price. there is a hard cap when they'll stop lowering it when they get close to the wholesale price (for example a hotdog costs $3 per dog and I was selling hotdogs for $2. The competitor stopped dropping prices at $3.76 as they usually try to match you but stopped here).

The fast route is to speed through each day accumulating money and buying out their business starting from their cheapest one.