Hopefully to put this to rest, a clearance is a clearance except for what level of classifcation. Rank, service, or affiliation is completely irrelevant. The government will decide what level of clearance you are eligible for, and the custodian of the material will determine your access based on kneed-to-know.
Once you have a clearance, it is reviewed and reinvestigated periodically. For secret, every 10 years, TS/SCI every 5 years. If something comes up (DWI, drugs, etc) on your reinvestigation (or at the time it happens), you can lose your eligibility or have it downgraded.
Financial deliquency is a big problem. It relfects on your trustworthiness and likelihood to blackmail/sale of material for financial need. You can shout at the rain all day about how unfair that is, but it's reality. I'm confident that the statistic bear them out on that.
As a security manager, I had to process several people for clearance issues. Several times it was not me who initiated the investigation. Your command will recieve a Letter of Intent that explains why the individual is going to lose his eligibility and what he/she can do to fight the action. It's a fairly painful process.
It's a new world in security since JPAS came out. It's a computer system that has everybody with a clearance on it. If something happens with you in relation to your clearance, DONCAF (The Man keeping you down) will know about it in very short order. Everybody else will find out the same day via JPAS. In short, if you screw up, you will lose your access very quickly and you are far less likely to "fall through the cracks" than before.