HAL is basically destined to fail.
The first issue is your choice of employees. If, for any reason, HAL starts to look successful, someone will copy the business model, but hire more traditionally valuable employees, yielding much better results. The only way this wont happen is if your disenfranchised-only approach yields some advantage which is sufficient to outweigh any disadvantages that might come from using a recruiting model that has generally not been found to be the best plan. We'll have to revisit this.
The second issue is construction. Your construction costs are going to be massive compared to normal construction costs. Your target construction workers have 0 work experience in the construction field. You are going to have to train them all, on the job. Now for most workers, this training comes with some price. You may pay an entry level worker less now, and they accept this because they know they are learning valuable information that will buy them entry into the higher paying jobs in the field. However, your construction workers are going to apply this skill once. They will not gain benefits from any apprenticeship that may happen.
Thus your construction workers will have to be paid with more perks than the average worker, and do sub-standard work due to a lack of experience and a lack of resolve. Any company which uses a normal business model will beat HAL out.
Now you hand them a new skill. This skill does indeed have long term applications, but do they want it? Does Convict_94293 happen to want to learn how to be a plumber? Does he have any drive at all to be a plumber? Or are you just filling a need for him? If you're just filling the need, then you can expect him to leave the instant you finish filling it, with no feeling of obligation on their part. Convicts are not known for loyalty into any system they don't see the benefit of.
So you have a few options. You can prevent them from leaving, which is covered in other answers. This is basically a bait and switch. Entice the criminals in, and then don't let them leave.
Another approach is to pay them enough to stay, in dollars, housing, etc. This is your suggestion. However, by definition this will have to be better pay than they can get elsewhere, so you will have to be overpaying all of your employees. If you had just used the normal employment process, it'd be easier!
The final approach is probably the only way this could work. Instill in them a desire to be part of a community. This is not easy. In fact, it is the opinion of many that the best systems we have in place for rehabilitating criminals don't do this successfully. You would have to do better.
So perhaps the answer is not a business model, but a person. Perhaps the CEO of HAL is an enigmatic fellow, bordering on cult leader, whose real goal is to raise up an entire cast of people. This particular individual would have that unstable charismatic something which causes people to not only follow, but want to follow. The purpose of HAL is not to build power plants, but to build a civilization built around this leader's principles.
Perhaps the leader is a woman. In this current age, we see very few CEOs with this sort of personal leadership. We also see very few female CEOs. In your story, perhaps these are not just correlated; they are causal. The addition of a particularly charismatic woman who could tie everyone together would fit the story, and it fits some of the the currently popular sterotypes of female leadership just enough that you could skirt along them while simultaneously defying stereotypes enough to make people think. The shift in leadership gender might be just enough to get readers to suspend disbelief long enough to give you time to write out what you think such a leader would need to be like.
It could be a fun story to try to craft. But no matter what, your leader is going to have to bring something very special to the table to balance out the massive downsides of this approach.