Photo storage consideration when buying new MBP

I'm about to buy a new late-2013 MPB but don't know what size SSD to get. I currently have a Windows laptop with a 640Gb HD of which easily half is taken up with photos. I could conceivably get away with a 512Gb SSD, but I'm sure that within a year or two that would be completely full, but the cost of a 1TB SSD makes me want to explore other solutions.

Is it possible to store my photos on a Time Capsule in a way that iPhoto (seamlessly) finds them (and saves new ones) there instead of locally on my MBP? Also because the TC backs up the MBP then does this lead to the photos being stored twice (therefore taking up twice the space)? If so then I'd have to think carefully between the 2Tb and 3Tb models.

Large amounts of photos, get an external hard drive. I have my iPhoto and Aperture apps pointed to a WD NAS drive (4TB) hooked up on my network for all my photos and videos.

You will need a large fast, USB3 will be fine, external hard drive. If your storage drive fails you lose everything, so you need to back that up too. Use carbon copy cloner to clone to an identical drive after any file editing or adding raw files, It will simply scan and only add new and changed files. Don't erase your cards until files are on both drives. The other option is a raid with built in redundancy, that minimises the risk, but it can still screw up or be stolen. Yet another option is a web based backup service. I've seen so many time machine backups screwed and not restoring I wouldn't personally trust them. Not an easy choice to make unless your photos have minimal value to you.