Home working in Bulgaria

You'll be lucky - those days are long gone: call centres here are full of young Bulgarians speaking perfect, or very close to perfect, English. WFH isn't really a thing here.

By and large, you'll need good expertise in a serious, and rare, field to find a job with just a command of English to offer on the linguistic side, I'm afraid. And the pay isn't exactly stellar either!

There's a Jobs section on the site: https://www.expat.com/en/jobs/europe/bulgaria/ The only real job there at present wants German speakers, the other appears more like they are recruiting paying students for an training course than actually offering paid work. But it's worth keeping an eye on that section in case something turns up. I believe you and your wife could also post a "work wanted" there listing your skills and qualifications. 

Unfortunately employers have to fill in a great deal of paperwork to employ foreign staff who need employment permits and D visas, so they're inclined to only take people offering a skill set they can't obtain locally. That or filling jobs in more internationally-oriented but lower-paid onsite work like hotel and hospitality.

Good luck with your search!

Jobs.bg is the go-to site for most job seekers, but companies are generally reluctant to have the hassle of sponsoring workers who don't already have a work permit - unless they have an in-demand skill.

@oopa

A formal full-time job offer is indeed one route to a D visa. It's possible, but, as @JimJ points out, it's rather challenging unless you're highly qualified. Remote jobs would be a toughie, as there are plenty of them around, but few coming with a full-time contract.

You can also be self-employed,and this requires some paperwork such as a business plan, and a basic level of Bulgarian language proficiency.

You can also do it by investment in property, but the amount is 300k euros, I think.

Unfortunately, Bulgaria doesn't yet have a D visa option for remote workers/digital nomads, or those of "independent means". Spain and Portugal have such options (e.g. D7 in Portugal and NLV in Spain) and so are quite popular for EU relocation. The NLV, for example, needs 30k euros in savings (or the equivalent in monthly passive income) so it's quite accessible. It's a non-working visa, but there are many who sneakily do remote work.