The langauge is irrelevant. Are you able to efine proper full test suites enale both sides to be completely tested independently? If not the rest does not matter.
What are you going to do when the whole thing doesn't hang together? Can very well happen no matter how many unit test are written and passed. Do you have the skill to write the specs for the interfaces to the required level of detail? If you are not an experienced programmer, it's very likely that you do not. It sounds to me like you are buying a lot of trouble and you are much better off finding somebody you can trust. As long as it doesn't produce liquidity issues, does it really matter if somebody else uses you idea? Especially if you can cut some sort of deal like permanent ongoing free support and troubleshooting.
Standard industry practice is the non-compete agreement. They're enforceable, except in places like California. Most firms pay for non-competition, though. Some don't, but the ones that don't typically have shorter agreements. There are some real dick-head companies that don't pay for up to 6 months, so for those places, I would advise programmers to avoid them altogether. Your contract should always pay you something for sitting out. As a matter of fact, I hope programmers start to reject these types of unpaid agreements or the courts start striking them down.
Most people aren't all that entrepreneurial, so I think your paranoia is only partially justified. 95% of people I know really just want a paycheck and time for them to spend with their families. I think $85/hr is a fair place to start for a competent programmer with a good track record, for someone with industry experience. I'd pay that, if I weren't paying his social security and healthcare benefits. Anything short of that is a waste of time for any programmer living in the US. One thing I'd like to mention to guys in the US: You will never be able to compete on cost, so be damned sure you're competing on quality.
In fact, the firm management often understands that extended unpaid non-compete term in their "standard" employment contract is unjustified and may agree to reduce it to the length of the notice period (which is one form of "paid" non-compete clause). There is no harm in asking.
Ok, so you want to split a project in two parts and dont even know how to describe the interface between the two? This is like one company building the front of a car, the other the back, and both neither talking to each other nor exchanging plans. The two parts WONT MATCH. Result: Wasted money. Componentized development is good, but it adds overhead and you start needing an architect.
My anecdotal experience agrees. Although I think some US freelancers have learned to do the same thing. Claim it will be done in 2 weeks, ahead of time, under budget. Then 2 weeks later the project is 2% complete because "Oh it was more complicated than we expected" and any assumed features that weren't part of the original contract are therefore (expensive) change requests. Note that multi-threading is notoriously hard to accomplish for inexperienced programmers. Your platform might work fine multi-threaded for trading 1 instrument for 1 hour during testing. Then in real time use when you're trading 100 instruments for 8 hours all of a sudden multi-threading becomes a serious problem that costs you serious $$$. You do get what you pay for. If you're looking to knock out a demo "proof of concept" type deal then any programmer will probably suffice. If you're looking for something professional, well architected, and thoroughly tested, that you can turn around and sell to others, you're going to have to pay for it. (I am a U.S. based C# software engineer with more then 13 years professional experience including outsource initiatives.)
I have built an EA with MT4 coder and it has 2 dlls and one of them has 4 functions. It worked perfectly. The dll is only for calculating the TP, SL,SIZE based on the inputs i entered in the input window. I gave symbols to every input the DLL has so no one of the 2 coders has any idea about what are these data and how it is processed. They know how to integrate the 2 parts. I had protected the DLL with a commercial software and handled it to the EA coder to test the whole EA. I know no protection is 100% secure. That is why i am trying to make the second project of ATS development by NOT EVEN HANDLING both parts to any coder. Because i have done with MT4 EA /C++ dll , I think i am able to do it again. Although the calculations this time is much complicated and the integration interfaces " input/output calls" are alittle bit more lengthy but i believe i could do it.
On wall street, full-time consultants are about $100 an hour on the low end (average developer with 5-10 yr experience). No overtime pay, calculated as 8hr a day. Those are us consultants, the oversea imports get paid a lot less, and outsource lesser still. You can roll the dice and hire some college grad for 200 bucks off the street, he might be a code wiz and a great job or have no idea how to write helloworld. Get a resume and ask them to code some trivial problems on the spot like binary tree traversal or fibonacci. If you need a thread expert, ask them to code some of the well known patterns like observer/producer+consumer. In my younger days, i used to interview by only asking tech questions, but find out a lot of developer (especially consultants) got the java book memorized and can talk very elegantly, then once you hire them and ask them to actually do the work, they cannot code worth shit. Now i just sat them down in front of an unconnected laptop with eclipse and mysql running, and ask them to code on the spot. Throws a lot of them off balance and weed out the posers which are many. It's not about getting the code perfect in the limited time, but how they write the code.