Yes it's simple to get a 3 months visa.. First many days before to move here, you apply online to have the papers for your visa,
here for ex. Then after 3 months you just extend (3 months again) your visa with a local agent. With the new law, you can extend your visa max 3 times then you have to leave the country (visa run) and come back with a new tourist visa. So you can stay : visa tourist (3 months) + 3 x extension (3x 3 months) = 1 year
For the apartments, very easy, it's like Thailand. You can rent for ex monthly with just one month deposit.
For the location, Saigon, Nha Trang, Da Nang, you can check too Vung Tau