Delegating software development work to freelancers

1. I use RentACoder.com. I have tried several others similar to it, and it is the best. The reason for this is that you can see how much you can trust a freelancer by his/her rating. If he has a high rating, not only has he been good in the past, he will also protect this rating for all it takes. I believe such a rating system is crucial if you want to outsource to someone you do not have a relation (indirect or direct) to.
2. Motivation is complicated and different from person to person. I believe that the best way is to try to understand the individual and what motives him/her.
3. What can you do? Try to get him back or get another one.
4. I believe SCRUM is not suited for freelancers. It values direct communication between the employees.

I would suggest you work with a service provider, not individual freelancers. Disclosure: I work for such a provider.

To your questions:

1. Request and check references.

2. Unless your work is intellectually challenging (your clients build something completely new or 2-5-10x better than existing offerings), I can think of no motivation other than money. I can think of many demotivations, though...

3. A reputable provider is much less likely to disappear completely. When a provider's employee quits, it is the provider's responsibility to minimize the impact.

I'm in remote consulting, so I can make answer from consultant perspective:

1. Start with Skype interview, check his linkedin/github/stackoverflow/blog/twitter, previous projects and references.
2. Interesting project or money. And, more important - understable project scope, goals and priorities; modern technologies, trust to developer, allow flexible schedule. And give him a chance to do what he thinks is best for your project (works only if you told him what you're doing, your goals, etc)
3. Hire only one who makes money on consulting, few years in row (not 'fresh out of college'), who is not looking for temporary job for few weeks while he is looking for real job.
4. Depends on. You can easily do daily skype stand-up, weekly iterations, etc. But not a 'planing poker', etc.

The best way to maintain off shore team is to start with small assignments and also have a skype interview with them. Check their previous rapport and skill set.

1. Always start with small module and see how they are giving you the results.

2. Do have 2-3 weekly scrum calls with team and also ask them to provide daily DSR.

3. Pay them as you go, on a milestone basis, once you are sure they have completed the module.