Let me say at the beginning I do not have personal or anecdotal knowledge of your prospective purchase.
The Holiday Rambler brand has a long and exemplary history is still churning out RV's and therefore has parts and a service network across the US. The Ford F-53 is the same.
Like anything made by imperfect humans, you will hear many opinions, positive and negative stories, and just plain wild conjecture on any given make/model of m/h. You'll have to decide how to separate fact from fiction.
Having said all that, you should pay close attention to the chassis for excessive corrosion, things that are hanging and dripping, prior owner modifications (the bane of buying a used vehicle of any type, particularly those "modifications" to electrical systems).
Like any heavy duty vehicle, have the operating systems thoroughly checked: brakes, batteries, generator, electrical distribution, hoses, clamps, belt(s), fluids, etc. Pay particular attention to any available service records on the drivetrain (transmission service, cooling system service, lube, oil changes, filters, etc.)
Look for indications on the undercarriage and chassis of tire failures, fatigue cracks, loose/missing bolts, fiberglas cracks/damage/repairs.
One you're happy with the skeleton, heart, and lungs, then the condition of the coach itself comes into play. And you'll be happy to remember that there are far less manufacturers of appliances than there are of motorhomes. This means that regardless of who sells the coach, most of the "guts" are non-denominational and parts/repair/replacements can be found at most reputable parts houses and service centers, even if they don't sell the HR brand.
So, as my uncle used to say: "Make haste slowly". Make a long and dispassionate inspection of your prospect, makes lists of questions for the seller, get professional opinions if you don't feel qualified to make technical evaluations yourself. In short (too late, I know
) it's a big used car. Proceed accordingly.
As to towing...you didn't say where you will normally operate. 5000lb is a hefty tow-load on any vehicle, but if you're operating a non-turbo powerplant in mountain country (or even steep foothills found around major river valleys) you may become frustrated with the load you're hauling. If it were me? I'd think about a lower calorie boat or a higher calorie powerplant (turbo diesel).
But that's just me.
Best of luck and happy trails