A good single parent source to start dating is http://singleparentsnetwork.com which not only recommends dating sites for single parents but has an online community, articles, and other resources. If you are a single parent and it doesn't matter if the other person is, you can try any dating site just be honest and upfront about your situation so your new potential mates knows what he/she is in for.
There are loads of websites that are good for single parents to start dating. Websites like match.com and eharmony are a good place to meet singles but for single parents who want to find other single parents specifically there is also singleparentlove.com
A Love Beyond Borders is a good international adoption agency that allows single parents to adopt.
Good places to meet other single parents in Portland are Single Parent Meet, Mingle 2 and Meet Up. Other good places are Examiner, Date Hookup and Amazing singles.
I don't know of any good Fitness communities online. You would have to go online to find out about the different Fitness communities, if they have any online.
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Schools like AIU and University of Phoenix have good online programs, but they are expensive. You might want to check with local community colleges in your area first to see what they offer. Many community colleges and universities have online classes.
A good place to meet single older women may be at social events for seniors, such as community center gatherings or senior citizen clubs. Online dating websites designed for older adults could also be a good avenue to connect with single older women. Additionally, taking classes or joining hobby groups tailored to older adults may provide opportunities to meet potential partners.
Check with the hospitals to find their recomendetions and through their friends who have retired.
Look online for local trade schools and community colleges.
Some good places to meet single seniors include community centers, senior centers, volunteer events, social clubs, and online dating sites designed for seniors. Attending classes or workshops, joining hobby groups or book clubs, and participating in local events are also great ways to interact with seniors in a more social setting.
It depends on the circumstances. There is no single correct answer to such questions