A landlord orally agreed to a set amount for monthly rent. He gave me the keys and told me to start moving my stuff in. The next day he Then told me he could get more for the place.
How do I stand?

Is a verbal agreement for rent amount binding?

I verbally agreed to a monthly rent. Landlord thinks I am too pushy so wants more for rent. Is this legal?

Depends on where you are at.. In China, nope, In the U.S. a verbal rental agreement can be changed with a 30 day notice in "most" places... So they can change the amount anytime they want, by giving you a notice... I say 30 days, it also depends on rental agreement, are you paying monthly ? Paying weekly ? Paying yearly?

Here, we pay our rent, one year in advance.. plus deposits... no such thing as monthly rent

Most likely, someone offered him a higher price... he has to let you move in, at the current price, but can change the price with notice.

As Chuck noted, he gave you the keys, that represents a contract. But since there is no lease you are a periodic tenant and the contract can be changed with proper notice.

So you have a choice to either move or pay the higher rent.

As indicated, it will depend on what state or country you are in. Assuming it is somewhere in the US, the LL can simply give you written notice of increased rent, &/or to move out.

Have you moved in yet? If your belongings are extensive, I would suggest you not move in, but find another place instead.