Claudia and Dennis Series:
Short series which focuses on the problems caused by money (or lack of it) in keeping horses. The first book was written with the well-known horsy author Rutherford Montgomery, although the sequel was written by Natlee Kenoyer alone.
1) A HORSE FOR CLAUDIA AND DENNIS
(With Rutherford Montgomery)
(DUELL, SLOANE & PEARCE [USA] 1958)
SUMMARY: Claudia and Dennis save up to buy their longed-for horse Blaze. But even when they get him they must still continue to earn money to keep him.
2) CLAUDIA'S FIVE DOLLAR HORSE
(DUELL, SLOANE & PEARCE [USA] 1960)
SUMMARY: With the family ranch in jeopardy due to lack of funds, Claudia may be ill-advised to spend five dollars buying a starving mare, but she can't abandon the horse to its fate. She decides to try and help save the ranch too by thinking up a scheme to make money by boarding horses and taking tourists on trail rides.
Reasonably easy to find in the USA via the internet. Can be very hard to find elsewhere.