UPDATE:  SBA disaster loans now available apply here: https://www.sba.gov/funding-programs/disaster-assistance 

We’re expecting that the Small Business Administration will declare Texas counties eligible for Economic Injury Disaster Loans as soon as Friday after Governor Abbott made the formal request.  You can track that designation on the SBA site.  More information on how to apply on the Texas Division of Emergency Management and you can fill out an economic injury sheet to submit to the SBA’s local disaster manager.

You can get ready to apply for these loans in advance by creating an online profile https://disasterloan.sba.gov/ela/Account/Register1 and beginning to prepare the required documents on page 2 of this sheet: https://disasterloan.sba.gov/ela/Documents/Three_Step_Process_SBA_Disaster_Loans.pdf which also has instructions for how to apply online.