Ideally hire an attorney to advise you and represent you. If you can't or won't do that, file your answer with the court. Note that any claims you have against the plaintiff that arise for the same transactions or occurences which form the basis of the complaint must be asserted now or lost. Handling a $20,000 case without counsel is not a good idea. Best wishes for a just and expeditious outcome.
I agree with the attorneys who have suggested you would be wise to hire counsel right away. There are many factors to consider, including but not limited to his much equity the proper owners of the property have, who the owner(s) are, what ability there is to shield the property from the claims of other creditors, what claims there are, etc.
The Constituion of the United States gives us all a right to not be put twice in jeopardy for the same offense. (Otherwise if prosecutors had it out for someone they could just keep trying an accused until they got a conviction.)
A MSJ can be filed any time that a party is able to argue that there are no issues of material fact. If the only issues are legal ones, SJ can be appropriate. In a foreclosure, there is almost always a MSJ and many are granted. If the other side thinks they have grounds for it, they are likely to pursue it since it may be cheaper than trial. I would not shy away from a MSJ based on the other side "kicking and screaming." I hope that helps. It's a general question so I can only give a...
That wouldn't be what happens in a civil case. Defendant would typically either move to dismiss, or to contest jurisdiction or would answer the allegations of the complaint and assert any defenses and counterclaims. In small claims, would go to the pretrial conference. If you are representing yourself, you probably should not be.