£1000 a year for an acre is not bad at all, we have a bit more than that and pay just less than double... it's viable if you can get say at least 30 drivers at a meeting once a week at £5 a head and a Regional will bring you from £500 to £1000 depending how busy your region is.
The big factor... outdoor racing can only sensibly take place for 6mths of the year and its weather that will always determine how many meetings you can get in within this time
for us as a club we are obviously still paying rent throughout the winter on the outdoor venue which is hardly used from end of September/beginning October until March so it makes winter racing more expensive as hosts when renting a second venue to do this... we have tried outdoor winter Sunday series but tbh it's always a big gamble with weather and temperatures particularly... racing isn't fun when your thumbs and feet are frozen stiff or soaked to the bone (as much as i prefer wet racing!)
You are always spending to run the venue and it always needs some sort of maintainence... building different track layouts is vitally important to keep the racers on their toes and give them different challenges too
Astro you will get for free if you shop around, we have contacts if needed... it costs around £150 per tonne minimum to dispose of used astro and you don't get many rolls to the tonne when its full of sand, worse if wet!
You do have to shop around for astro... far too many variations of pile, colour, weave for different sports its used for etc... you may find you have to pay a gesture towards fuel costs with haulage of it... but its normally available by a very big lorry load, which you will probably find would cover enough area to build 3 1/8th nitro sized tracks!
As for planning, we were very lucky... our landlord is a gentleman farmer and also a local councillor, as there was already planning for the MX track on same site we had no issues as it was all in place.... even noise permissions for running nitro cars (they are louder than a 2 stroke race MX bike surprisingly... which is why they should be banned

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If planning a track venture... factor in a very sensible amount of car parking/pitting and factor in costs of making it a decent surface... racers take a huge space up with car/van loads of kit, tents/gazebos etc when you try and work out space for say a 120 driver meeting it soon gets swallowed up... the surface is important as its more user friendly to not get covered in mud, especially some of the more fashionable younger racers with their trendy designer clobber!
If it is to be built on a field... drainage is a massive consideration... if you spend a good few thousand building a lovely track to ind it floods when it drizzles then you'll only have to rip it up again to sort drainage and build land up so it drains.... something A1 Racing Club had to do with 100's of tonnes of topsoil to raise levels of track as land is heavy grey clay and was good for making lakes when it rained.
Also, heavy traffic from racers and their heavy vans/cars can soon wear/damage the land/pitting area rendering it useless when wet, especially if your venue is busy... again another very costly affair to fix... if you do manage to get lots and lots of Astro then this could make a good surface for pitting/car parking but you still need a sensible base underneath for drainage and heavy vehicles.
A rostrum can be a very expensive affair too, it cost us over £1k last year to build a shipping container/scaffold type rostrum with steps and we already had container on site for storage! it was still cheap really as its rock solid an safe (something else that will cost you thousands when the health and safety comes into it... particularly if building tracks on council property with any sort of public access)
Don't forget your track markings, can cost silly amounts as the cheaper hoses/pipes etc tend to go fragile with UV and weather, plus consider how tracks will be laid and the speed of laying them... labour intensive track changes soon wear thin when it takes most of a day for small gang to do it.
Toilets cost us a fair chunk each year, we have no running water so use portaloos, the club owns the loos but has to pay to get them emptied and that is quite often if running busy meetings!
We don't have mains power so have to use generators to power race control and our flood lighting we installed last winter (so you can race a bit longer when the nights draw in at end of summer... plus potential for a 24hr endurance offroad meeting in pipeline

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Fuel costs for running these changes daily atm and intial purchase of gennys!
A massive issue if starting a club from scratch these days... Timing Kit/Transponders, can be very costly and pretty hard to find these days as most established clubs are on the hunt for good back up sets as they can't be bought new and don't last forever, even though they can repaired or have batteries replaced they can die eventually ... timing software is another purchase that costs a club too. Computer, PA system, cabling, printer, ink, paper, race numbers, websites, trophies, fluro bibs, safety fencing etc etc... all costs of running decent meetings to recognised standards.
Most important of all... work in harmony with your existing local clubs, don't treat them as competition, chat to them regarding dates of meetings and consider that their members can also be your members and vice versa if you don't clash meetings... if you network together and help each other out it becomes great if you have a crisis and need to borrow timing kit, run out of race numbers at last minute or something required to run a meeting... its all about back scratching and learning from each other.
The clubs, organisers and racers in Mid-East Region have all been fantastic with us and very supportive in getting us established with racing 1/10th electric classes and guiding us through our first year with Regionals last year, all run by very nice helpful people and all approachable and offer help and experienced advice without begging or stressing! (so thanks guys if you are reading this, you are all stars

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At the end of the day a lot of us club organisers are also keen racers, so will encourage new tracks and help spread word as we ourselves like to go to new venues to race (when we race elsewhere it is our time off from running meetings/working so can just play with cars whilst someone else has to work!)