Closing on my first duplex Friday! Any tips/advice for 1st timer?

[Troy Seals]

What are the things you wish you would have known starting as a first time landlord.  I'm closing on a duplex soon, which will be my first real estate purchase.  Just looking for any advice on managing a rental, from bookkeeping, to managing tenants, to documents, etc.  Any help will be much appreciated.  The property has been owner occupied for the last 30 years and has been well maintained.  The current tenant has lived there 10+ years but I suspect that's mostly because they are paying well below market rate for their rent.  They are paying $800/month until their lease runs out in January.  Market rate for a similar 3 bed rental is about $1100 in my area.  I will definitely be raising the rent but is it worth it to work with them and maybe take slightly less than the market rate since they have been long term tenants? That's just one of the questions I've been thinking about.  Thanks in advance!