I would like to have a database that:
stores all the property addresses and names in all counties in only a single state, so efficiency is a factor.
allows for multiple people to access the database at the same time and make changes to it.
is installed on multiple computers, so price is a factor
has a relatively small learning curve
is compatible with excel, since a lot of calculations to manipulate strings (e.g. addresses) is necessary before info is imported into database, UNLESS the database has similar functions like excel to manipulate content, such as splitting addresses based on spaces or delimiters and being able to compare and match two files of content and do something if there's a match
has the ability to import columns from excel and translate them into fields, if the fields do not exist, and if they do, then to update the value of the fields
has some kind of ability to measure success of a marketing campaign

Does anyone know of a database that best suits these needs?

Thanks for response.