Ideally, I would like to have my laptops' lids closed and still fully operate them (e.g. video, audio, navigation etc), would that be possible?

Make up your mind, original post says control both from one which implies one has its screen open ... for which you were given various free software solutions, (which you haven't bothered to try).

Now you want both laptop screens closed, for which the only way you're going to get a cheap solution is if someone gives you: a KVM, a monitor, a keyboard, a mouse, and a USB hub.

Get off your butt, go down the Op Shops, (charity shops), and you'll probably find everything except the KVM.

I read the post that the intention was to  run one laptop from another laptop.  There  are some good solutions mentioned already, but I figured I would add a few more building on what has been said. 

Most monitors have more than one display input.  Like a 2 hdmi or 1 hdmi and 1 vga.  You can easily get  adapters to help if the laptop does not have a matching output. You can toggle between displays using the monitor's menu and sometimes using a hotkey in conjunction with a utility provided by the monitor manufacturer. I think some LG monitors  have this kind of utilities.  A few newer monitors have a usb switch built usb switch, but you can also buy one really cheap.  ( I think someone else mentioned the usb switch in the thread) This mimics the kvm.  Kvms are pretty cheap nowadays.

As an aside, Windows 10 also provides the ability to Project a screen on another windows 10 system on the network. This could help if you were trying to run both laptops from one of the laptops.  How to use screen mirroring on Windows 10 to turn your PC into a wireless display

I know a few people who  use the project screen instead of something like anydesk or ultravnc.