Virtual Box needs 64 bit laptop, right?
First let’s discuss what do you mean by a 64 bit laptop/desktop? Do you mean OS or Hardware?
Almost all the Desktop/Laptop Hardware manufactured in last 5-6 years is 64 bit compatible. It can run both 32 bit and 64 bit OS. The desktop or the laptop that you might be using today is 64 bit compatible, but you might be running a 32 bit OS. Upgrade to 64 bit OS and the same Windows license key can be used.
For my SharePoint 2010 environments, I have upgraded a couple of desktops/laptops to 64 bit OS in past few years. I able to do it successfully on all but one laptop (Lenevo T60, 6 to 8 years old), which don’t have 64 bit compatible CPU.
Now coming to the question, whether Virtual Box requires 64 bit OS. As per documentation, it works on both 32 bit and 64 bit OS.
Can I run 32 bit Guest VM on 64 bit Host OS?
Yes, Both 32 bit and 64 bit Guest VM’s can be setup. Both Hyper-V and Virtual Box will allow that.
Can I run 64 bit Guest VM on 32 bit Host OS?
Yes for Virtual Box, under certain conditions documented below.
Hyper-V on Windows 8 is not available for 32 bit OS.