Programming for iOS in virtual machine is feasible?

It may even technically achieve, but the license does not allow doing this. It is only possible to run an iOS simulator and generate the application of an Apple machine. You can even use a VM, but it has to be running on a Mac.

You can use some service that provides you with a VM running on a Mac. Visual Studio Enterprise provides something, it has other Mac cloud services. See:

• Xamarin Test Cloud
• Mac in Cloud

You'll have a better experience with the Mac itself. It pays off only you can say.

I used VirtualBox to test what it is like to program in Swift, it took me a long time to get MAC OS X running, at the time I think it was Yosemite or El Capitan that I installed.

After installing it took a long time to get Xcode installed as well, and when I finally got it, it worked fine, without many traps etc.

My biggest problem was with screen size in the virtualbox, I could not leave the screen full and had to be using scrollbar, in addition some MAC commands that I could not find on my "standard" keyboard were also a problem for me.

Summarizing

It is possible to program in swift using sim virtualbox. But it is an experience far from pleasant. With regards to application deploy, I can not say for sure but it is probable that you can not do it using VM.

My suggestion is to buy a MAC used by olx, mercadolivre etc ... And use it until you can get money to buy a new one with a better configuration.