Should you purchase round-trip ticket for visitor visa?

[immihelp]

Hello,

I have a quick question on entry to the U.S. My friend recently obtained a B2 Visitors Visa to the US. It is a multi-entry and length is stay is 6months per visit. My question is when my friend visits me, should she buy a round-trip ticket or one-way and then buy the return ticket later on?

How does this impact the length of stay for her in the US?

Thanks

[immihelp]

Round trip ticket. Otherwise, the officer at the port of entry may think the person is not planning to go back at all and may not allow to enter at all.