What are the rules for using "есть" when expressing possession (to have)?
I pulled the following examples from another forum.

Quote Originally Posted by Анатолий Д
I am not sure whether there are any rules on this issue.
It's one of those things that a native speaker acquires unconsciously.

Examples when you need or don't need "есть" in Russian:

You have an opportunity, a choice, - у вас есть возможность, у вас есть выбор.

He has a true friend - у него есть настоящий друг
He has many friends - у него много друзей

He has a car - у него есть машина
He has a new car now - у него теперь новая машина

He has two kids - у него двое детей
He has a cat - у него есть кошка

It looks like it is hard to figure out a rule

The following use "есть" because the direct object is singular.

You have a choice - у вас есть выбор.
He has a friend - у него есть друг
He has a car - у него есть машина
He has a cat - у него есть кошка

The following do NOT use "есть" because the direct object is plural.

He has many friends - у него много друзей
He has two kids - у него двое детей


But why do you omit "есть" here?

He has a new car now - у него теперь новая машина