once I get a text telling me that this person is interested for my vehicle, what do I do now?

Be patient if the offer or is really interest they will contact you again. If not then they were not very interested. You can email them back and ask them if they would like to make an offer or if they have any questions. This is a good way to weed out people who are not really interested or do not have the funds to purchase the vechical. Someone who is really interested will usually give their phone number so you can call them.