It’s a one.

To make it two you would write it like:

I read. He studied at my house.

I

read at my house. What does this mean to me? He studied in my house.

But to do this would be unnecessary and perhaps come across a little clumsy.

So, be honest, we have a choice.

It is a sentence consisting of two finite clauses connected (conjoined) with the conjunction and. Very often a comma will go before the and (or other conjunction), as in

I read, and he studied at my house.

The first finite clause ( I read ) is so short that a comma shouldn’t be needed. If before and if the finite clause

is not short then the comma would be used if the answer is said in the following

sentence: “I read twenty books in between 7pm to 10pm on Wednesday, and he studied at my house” This sentence is what I do when I’m writing two sentence with the same sentence. If the whole thing is still one sentence with two finite clauses (the verb in each clause is finite: read, studied, etc.) notice that

the whole thing is still one sentence with two finite clauses.