Classifying as a rental property vs. classifying as a second home

[Andy Winningham]

Hello. Question for the community. I'm a financial planner in Dallas, TX and I've got a client who is considering the following decision and I'd love to hear some wisdom about how to advise him to proceed. 

Situation. He and his wife are likely going to buy her parents' home in El Paso, TX next year and continue to rent it out to them. He says that real estate investor friends of his have advised him that he can get this home classified as a second home rather than as a rental property and that that treatment is preferable to it being classified as a rental. I have two questions...

1). Is he right? Can he classify this as a second home? Her parents would be paying them rent like any other tenant. I imagine he and his wife would stay there whenever they visited her family, which is probably a few weeks each year. 

2). Is that even a good idea? All things considered, is it even better for them to have it classified as a second home? Or would a rental property be more favorable?