Hi Heather !
Real estate rental is variable in the area of "Hte-Savoie", as everywhere in france since the crisis begun.
Last months there was a new general set-back - at least a slow decline of prices.
But all of the question depends of which segment of the market you're talking about. I mean with some kind of properties prices are stable, with others it's a real drop and some may even rise up.
Instead of trying to "feel" yourself how is the market , asking people for advices I think you'd better have a try with official statistics delivred by CCI ( Chambre de Commerce International located in Fernay-Voltaire close to Geneva) ; or ask INSEE ( National Stat Sce called "Institut National de statistiques & études économiques"). Or, local association of owners on departement 74 - They probably all have a lot of info about your topic. And ... It's free !
Talking about locations and prices you'll understand quickly where to buy and where not to buy a property. Touristic zones such as suroundings of Mont-Blanc and valley around, are probably the best especially considering the fact they will provide occupation at least 4/6 months during winter and 3/4 during summer. At least... On other parts of area concerned it depends on which kind of occupation (and tenants) you are in search of. Are they tourists or whole year long term of tenancy ?
This will answer to your question " rent out in the summer as well as winter season ?"
Considering what you said about real estate agents - I have no sympathy with : I was a building surveyor previously - it's true but it's their job ! what are you expecting from a guy practising this kind of job ?
In France organisation, basic and historical culture of real estate is totally different than in anglo-saxon countries. Totally another world. There are a lot of "traps" and snaggs to be discovered before acquiring a property for sure . But there is no neutral profession who is in charge - officially - to give advice on a very general point of view - such as technical audit, valuation of the property, estimation of renovation works compared to compliance with rules, judiciary advice and contentious business and claims of all sort followings.
All things which are set in a frame of mission, with reports. And following missions can run one after one.
French don't have - curiously consedering the amount of an acquisition, - this practice at all, about real estate affairs. it's not the use. Even if it's really a lot of complex, specific , and diversified topics real estate in this country ! - You can trust me !- And making a synthesis about a property is a serious job.
The habit is to trust ... the agent who is selling a property ! no neutral advice.
So try to make that job ( about searching info on which kind of rental income provides this or this kind of property) with serious threads and links with other owners. Take a map , study the best locations, then go on the field visiting the full area, and let's build your own opinion.
Good luck , heather !