I've been using
Gnucash and I like it.
It's a completely free full-fledged double-entry accounting system, so you'll need to understand the basics of accounting to be able to use it, but then again, you'll need to understand them anyway if you're going to do your own thing. Works best on Linux but they've got a Windows version too; not the prettiest-looking software around, but it's rock solid and handles multiple currencies easily (wrapping your own head around them is the hard part...).
Basic bookkeeping services in Sing start from a few hundred dollars/month and the end of financial year accounting & taxes will set you back around a thousand. I keep my own books, because I'm a control freak and like to know exactly where I stand at any given moment, but I let the pros compile annual reports, taxes etc, because it's a lot of boring paperwork where mistakes could get very, very expensive.