Seth Berman Head of Growth Marketing at Stripe

I ran direct marketing for a Medicare health plan and, before that, marketed long term care insurance so I have quite a bit of expertise in reaching an older audience.

One option is to craft a special offer for AARP or a to offer to its membership - http://discounts.aarp.org/category/supercategory/categoryId/727/subCategoryId/674/uSource/HCTN

Also, I would look broadly at what ancestry.com is doing, as its users tend to be older females. You'll note Ancestry offers a discount to AARP members, and maybe Ancestry.com itself would be interested in a partnership.

If you'd like to discuss these ideas, and others, in more detail, you can schedule a call with me.

An easy and free way to test the popularity of specific keywords is to use google.com/trends. You can enter up to 5 keywords at a time and compare search interest in them over time. Then you could select a domain name based on the most popular keyword available as a domain name.

Google Consumer Surveys are very low cost. Although they are designed for B2C rather than B2B, you can ask qualifying questions, and it may be a way for you to get responses from marketers.
http://www.google.com/insights/consumersurveys/home

Fiksu is another option although it has a minimum budget required to work with them. Fiksu uses its proprietary optimization engine across a number of mobile ad networks to maximize return based on your specific objectives.

In a B2C scenario, I've seen this done by leveraging user acquisition to generate leads for third parties. You can monetize the registration flow by adding these partner offers and keep the difference between what it costs to acquire a user and what you can sell the leads for.

In B2B, demand generation teams have become very effective at measuring the impact of their activities in sales with the help of marketing and sales automation platforms. While the revenue typically doesn't sit on the marketing team's P&L, they are able to demonstrate that their marketing activities are profitable for the business.

Tactically you could set up a one-page site using populr.me linked to a Google docs form to collect email addresses. As Bruce mentioned, ideally you would have something to offer in exchange for people providing you with their email address, but you could also have the page be a teaser of what's to come and have the users subscribe to get updates on your product launch, new content, or whatever it is you are building.