You can pickup a R9-380X for NewEgg for $215, free shipping:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814125836&ignorebbr=1 also has a $10 rebate (limit 1) to knock it down to $205.
As far as recommending the older cards, yes they will work and if you are worried about only the initial investment they might work out better if you can get a good price. Unfortunately,with the resurgence of GPU mining, even the used market has gone up in price quite a bit.
One thing to consider though, is with a new card such as the linked R9-380x, it will retain a higher resale value and will come with a manufacturers warranty. The Gigabyte model listed comes with 3 years, so assuming you use it to mine for a year, you can offer peace of mind to the subsequent purchaser which will also fetch a slightly higher price.
If you go used, putting another year on an already used card that is out of manufacturers warranty will probably be close to worthless for resale by the time you decide to get rid of it. So if you do go used, make sure it is at a decent discount, at least by half of its original cost. So comparing it to the card I linked above, you would need to pick up a used R9-280X for less than $107.50 shipped. Of course the used card would probably be out of the warranty period and if it was used for mining before the components may already be stressed to the point of failing the first time it gets a bit warm or a power surge rolls through (think thunder storm), etc.
Anyway, if you can swing it I am thinking sticking with new cards with the intent of reselling them later is the best. Just be sure to keep this in mind and keep all the boxes, accessories, connectors, etc. tucked safely away and in good condition.
