Without wanting to sound too stupid, SQL Express is free and the free resources make it a good choice for a beginner like me. I know it has limitations (read other posts) but the figures mean little to me I'm afraid. 

* Can anyone give me ball park figures on the number of users it can handle? I'm looking at possibly 40-50 users maximum, carrying out CRUD operations to a simple 8 table database.

I imagine I'll be querying my DB a lot so my users can generate reports, but again I wouldn't think (hope) they are to complicated or demanding - simple select and filter on user name queries. Obviously I'll run these past StackOverflow to see if they can be written more effectively (and to see what an effective query looks like).

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Thanks for all the comments. I've got a better understanding of what things I need to consider to make sure that the free version is enough - good coding practices, efficient queries and closing connections down after use.

I believe my users will it hit moderately, and they shouldn't generate much data as I'm going to limit what we capture to the basics. Later on should I develop my solution I'll mention the fact of limitations to my bosses and it'll be their decision whether to pay or keep nit limited.

Apologies for the limited information in the question, and the 'answering my own question' option but rather than reply to you all I thought this was most effective.