How to bootstrap a portal?

We usually refer to this as 'seeding' your site.

So, don't have your site setup initially for people to browse and search an empty site. Keep it a landing page describing the site and say it launches in two weeks or whatever and have a way for people to add their email to get notified when it launches.

But have a button to add your property for free NOW!

Then to get people to the site you could try a couple of these options that have worked for me in the past.

• If there are competitors in this space visit their websites and contact people listed on the site to come list on your site for free for X days and say it's a $Y value. Giving something for free isn't that cool anymore ;) but if you say it's a $99 value then they might be willing to do it.
• If you can or if it makes sense for your site add the listings yourself. By property I am imagining this is some home listing, rental or vacation properties? So that might be harder to seed yourself as you would need contact info and probably should have permission. But some systems you can get away with just adding in data yourself from directories, yellow pages etc. (but might not work for you)
• You can hire a cold call company for about $2,000 a month that you can give them a task and they'll call people 8 hours a day. So you could have them browse directories, calling contacts and suggest they list on your site.
• Google Ads probably won't work for seeding your database
• Check craigslist and other places where people are listing properties and get in touch.

ALSO - if doing something like properties it's VERY hard to launch nationally day one. So you may have to grow it city, county, state. Craigslist didn't start day one nationally. Most websites don't. They have a huge following in a certain area then grow out bigger.

Good luck!

Contact lots of potential users, explaining why your portal is better than others, and convince them to add listings to it (for free obviously).

Contact potential users, as Dario said, and tell them that you have developed a new property portal. Tell them that the site is not live yet, but that you are looking for property listings to put on the site before it launches. Ask them for the basic information needed to make a posting on your site, and ask if it would be ok to make a post under their name with the information they provided. Its going to be hit or miss, but I am sure some people will respond positively to you. That way when you actually launch the site, there is some content on there and it doesn't look as empty. Then, let them know when you actually put the site up on the internet. Also, a good idea would be to have some screen shots maybe of the site, to help give them an idea of what it looks like.