Participants in the Microsoft Office Live adManager Beta can fire up their search campaigns by purchasing ads for display on MSN and Live Search, and on Ask Sponsored Listings.

Microsoft’s Office Live provides three options for business owners to build their websites and implement optional productivity tools. Naturally, Microsoft would love to see those entrepreneurs take part in its adCenter online advertising service.

The company has sweetened the offer. Barry Schwartz at Search Engine Land noted the pairing of Microsoft and Ask to sell search advertising on both of those networks from one place, the Microsoft Office Live adManager Beta.

Schwartz said this is the first time in five years that two of the top five search engines have paired on a search engine advertising deal. Business site publishers start with a $50 credit when joining the adManager Beta, with their ads appearing in results at the two search sites.

Ads on Ask appear in search results and in other sites in Ask’s publisher network. An IAC search marketing general manager told Schwartz the Ask Sponsored Listings product reaches over 59 million unique visitors per month.

Business owners considering the plan will want to think about such reach, while keeping in mind the market shares of the main search engines. Combined, MSN/Live Search and Ask reach fewer people per month than second place Yahoo by itself, let alone search leader Google.

If the adManager Beta can deliver a good return on the cost-per-click ads they run across the two networks, business owners should be happy with the results. But if the costs outweigh the return, those ad buyers will flee to other options, especially since marketers can easily run multiple campaigns for online advertising.