Hola Shirley,

"Irse" means to go away or to go off ..... so: "My parents were going around saying that they were going [off / away] to buy a house at the beach." So its not about an intention "they are going to buy" but more about the action of leaving where they are in order to buy." At least this is the meaning I take from it.

I find the dictionary in "WordReference" really helpful for working out some of these meanings; it's worth a try. Using it on a phone is awkward but on a tablet or laptop is fairly easy. 

Saludos. John

It's not irse, but comprarse.  We could also write it like this:  "iban a comprarse".  Here the reflexive is used for emphasis.  You might be able to find the Kwiziq lesson on this.

from what i learnt, reflexive pronouns are used when speaking of possession of things. so comprarse instead of comprar is used.