万变不离其宗。

landlord must understand the basic of bookkeeping/accounting,behind the scene, in order to opt right software application to keep track of daily business activities.

it all depends on individual's preference and the nature of business (solo, S. LLP, etc).

nothing is wrong startng w/ Excel which is pretty 直观。

my suggestion is to set up your own system well.  the rest of job is just data entry which even your kids can do it for you.

last but not least, keep all your receipts or evidence for every single transaction.