Who We Are


With over twenty years of experience as a tax attorney and accountant and founder of Cain Advisory Group (CAG) Brian Cain provides tax preparation/planning and financial consulting for small businesses, entrepreneurs and individuals. 


Outside of work, Brian loves to travel and see as much of the world as possible with his beautiful wife Sandra and two daughters. Recently the family enjoyed a three-year stay in Italy, where Sandra was stationed as a civilian attorney for the US Navy. During that time, he and his family visited over 26 countries! Brian continued to work remotely from Italy.  A good amount of travelling was required to guarantee ongoing service for his clients.  During the second year in Italy, he took 9 trips back to the US! That’s over 57,438 miles! 


Brian returned to San Diego in January of 2020 and his family joined later that year.  Sandra is currently head of the legal office at Navy Region Southwest and his daughters are busy in school and being teenagers!

Meet the Team!

Marie Nelson – Marie is our senior level tax preparer with six years as a tax professional and Enrolled Agent (EA). She completed her undergraduate degree at UC Riverside and, while currently on hiatus, attended San Diego State for MS in Accountancy and MBA for 2 years. Marie loves challenging tax questions and takes great pride and satisfaction in helping clients! On her off time, she enjoys gardening, attending music and art festivals and going to live concerts! 

Mary Vanston – Mary is a Certified QuickBooks Advisor and has been in accounting for over twenty years. She is a long-time member of Brian’s team serving his clients as the full charge bookkeeper. When Mary is not working, she is “still working”, dividing her time between the office and her home office. She loves Nascar and is a huge fan of Kyle Bush, baking is her passion (especially cupcakes), she is a collector of eclectic miniatures and loves to travel by train.

Jill Ostland – Jill is the newest addition to the team. Officially her title is Executive Assistant, but as she grows into the role, she will be wearing many different hats! Coming to us with administrative and customer service experience, she is always ready to assist you! Please call her with your questions or just to introduce yourself! Jill and her husband Vaughn have 3 boys and a cat! She loves to watch hockey (her favorite team is the Toronto Maple Leafs), swim Masters at 6am, play pickleball, cook, and spend time with family.

Donna Thaidigsman – Donna is a huge asset to the Cain group team as we welcome the Losnick clients to Cain Advisory Group. Always happy to jump in on any project, she is integral to ensuring a smooth transition for the Cain Advisory group team and clients alike. An avid sailor, Donna and her husband love to race their 37’ sailboat and pick up trophies as often as possible! She also enjoys traveling, reading, walking and being with friends.

Brian Cain– He has over 21 years as a Tax attorney and tax accountant, Brian is the founder of CAG. Through his career he has always run his practice as an accounting firm rather than a law firm. He enjoys working in all aspects of tax and providing additional value as an attorney to his clients. Outside of work, traveling with his beautiful family, hiking (his bucket list includes hiking The Pacific Crest National Scenic Trail (PCT), and being out on his boat!