Q. What can i do to keep it running great?
Oil changes at 3,000 miles. Since there's almost no miles on it, run synthetic.
Air filter changes every 12,000 to 15,000 miles.
Transmission fluid drain and fills every 15,000 miles.
Radiator flush at 30,000 miles.

It doesn't take much to keep these cars going well past 100K.

Q. what can i do to maybe add a little hp without a ton of money and no visible changes?
"little" is the key word here. I would do with an AEM short ram intake. It provides a washable cone filter and will actually save you money in the long run.

Q. what are some problems i can expect to have with the car (IE: maintanence)
Looks like you got an LX i4. You can expect your typical maintanence parts to go over time, but this happens with every car.

Suspension:
- brakes go at 50K
- rotors, pending stopping habbits, can go to 80K+

Powertrain:
- don't hammer your automatic trans. don't neutral drop. don't expect to launch like a Viper from a red light. Keep the accelleration normal and your transmission will be fine.
- Sparkplugs and wires need to go at 90K, same with the water pump.

The only real "problem" I've heard about are dying alternators and O2 sensors ... nothing too serious.