maintain (oneself or someone) in (something)
To allow oneself or someone to live a particular lifestyle. Unfortunately, we don't have enough money to maintain ourselves in this lavish manse anymore.
maintain (something) at (something)
To keep something at a particular setting or level. I try to maintain my savings at $1,000, at least, in case of emergencies.
maintain someone in something
to keep or provide for someone in a certain style or condition. I insist that you maintain me in the style to which I have become accustomed. He had hoped to maintain himself in comfort.
maintain something at something
to keep something at a certain level, setting, degree, amount, etc. You must maintain the temperature at 30 degrees Celsius. We have to maintain the temperature at a very high level.