回复：it's your choice to use it as rental or primary; if you use i

primary, there is no impact on your loan rate for the primary you are about to buy; However, you may not be qualified for early withdraw from retirement accounts without penalty.

For your relative, if the property fair value is no more than $130,000; then the COUPLE do not need to pay gift tax conditioning that they can't give you any more gift in coming 5 years.If it is over $130k, then they need to set up "Grantor Retained Interest Unit Trust" to avoid gift tax. This also applies to those "poor" parents who are considering transfer some properties to their kids. 

ongratulations!! You are luckier than most of landlords here :>)