Founder of few companies, worked as CTO in some more, advised a lot of them. 14 years experience working in Fortune 500 mixed with Start-Up & VC ecosystem first hand experience alongside.
If it is really only two way country transfer (or one receiving country and several country stacks sending money there) it would be best to build your own custom solution.
Basically a simple SW to allow for receive electronic transfer money in some region (one for EU, one for US, one for Australia for example) together with API linked bank accounts and one payout in target country.
Of course you might have to do some KYC/AML/PEP checks but there are API avaliable services to do that for you.
Depending on how you want to build it, it should not cost you more then 75k USD total.
Ask around for good SW houses in your area or call me and I can help you put it up together.
Not easily answered without further info, best way for you to approach it would be to use comparatible service (be it shopify, attlasian, wix) and do your own market research on potential customer base as well as CVL.
If you need help it would be fun to digg in, did a lot of research in this area for startups I was working my DD magic on.
1. Contract, contract, contract. Both with the client to avoid going directly under severe penalties, both for employees (even subcontracting entities or freelancers) to scare them off such behaviour. And of course, keep your guys happy and on interesting projects, that will help nowadays more then any penalties.
2. No. Either you're end to end responsible for the development and your contract says so (and allows you for subcontractors) or you're only providing on top of cream management service, in that case they should have separate contract with those guys.
3. Design, Scalling architecture, marketing mix, R&D....you can add a lot of flavour into this. Depends on your skillset.
4. A lot. One of my companies was focused as "Foundation house", project based only, including full business development & planning services, goverment discussions around regulatory issues and management of other third parties.
Call me if you want more info, that's quite a broad topic and you probably need to have it sorted to have good client value proposition.
As I worked in this industry both in other people companies and my own as well I would definitely stick with 3 major areas:
1. Word of mouth: people and companies in this business usually know each other, start with the smaller ones you can reach in your network, ask them for reference and testimonial, let them spread the info.
2. Promoted reviews and Linkedin influencers, again try starting with small/local/regional people/magazines in SaaS/Software area, offer them free trial.
3. Targeted campaigns and provocative comparison, usual cold mail selling will not get you there
(probably), so try target your potential customer base with smaller advertising campaigns, precisely focused.