Why did I pick this sub niche? I grew up in the 60's and while I don't really know anything about fashion per say, I do know what the girls were wearing back then because I was always staring at them with my tongue hanging out of my mouth. So I know what to look for online as far as items that maybe I could sell.
The next thing we want to do is get ourselves a web site for our niche. So we can go to GoDaddy or wherever and look up a few names. The first one I came up with was 60sfashions.com. It wasn't available so I simply inserted a hyphen between 60s and fashions and voila. I had a web site. No, I didn't register it so you can still get it.
But what I did do was go to www.60sfashions.com to see how the monetized the site.
The site itself didn't seem to really cater to 60s fashions in particular but to clothes in general, and lots of clothes. So I then went back to Google to see what paid ads were showing for that keyword phrase.
I found Target and Ebay and that's it. This is a market that simply hasn't been exploited yet. Okay, so how do we exploit it?
Well, off the top of my head, I can think of one way. Get a hold of a wholesaler that specializes in nostalgic clothing. See if you can get a good supply of items and throw them up on your site. The market may very well be there with that many monthly searches.
If you're unsure, one way to be sure is simply to put up a survey on your site before you do anything else asking people what it is about 60s fashions that they're interested in. Ask specifically if they'd be interested in purchasing 60s style clothing.
You may find out that they're interested in 60s fashion photos. Great! Go get some magazines from the 60s, which are no hard to do when going to nostalgic magazine stores, and put up famous photos for sale.
If you sit down and really put some thought into this, you can come up with a way to monetize 60s fashion.