When I was racing Mods I got tow money added to the payout. Not true at all tracks. Only spent around $100 - 125 per night (baring no major setbacks ; broken engines, Crashes, Tow Vehicle break downs, etc...).
Pavement Modifieds are big (with a capital BIG) money. $20,000 + for roller and minimum of $10,000 for an engine.
I haven't raced now for a few years. Costs are up on fuel and oil. So, like Thunder said; it's a hard question to give an exact answer. Tracks are different as to what they pay. Costs for everything are up. That's the major factor for me going to to a smaller, more cost effective, forms of racing. That, and I like the idea of using a bike engine to power a car. Something I have toyed with 'til I took the plunge to build my own car. Rather than a street driven oddity; I wanted something I could race. I'm still working on that! Things are much closer than 10 years ago.
If you can get sponsors to cover ANY of the costs; then you are ahead of the game. You will need to sell ANY sponsor, on What YOU Can Do For Them!!!! Advertising!!!! That's what it's all about. Be willing to park your car out front of his business (SURE TO DRAW A CROWD), Answer Questions, Decals, Paint, Etc............. ALL Dependant on Costs VS What The Sponsor Is Willing To Pay to attract business HIS way. You need to sell him on YOU!!!
Over the course of 30 years in business for myself, I have sponsored several cars. Some of my own cars were tax deductable. ALL of what I spent on others was deductable as advertising. You HAVE to be Willing; And Able; to provide advertising for your sponsors. Trust Me - They will ALWAYS ask at the worst possible times!
If your sponsor can part with $1500; That's $1500 you don't have to spend Out Of Pocket. Right now, I'm in for over $6,000 (long story) ALL out of my own pocket. No tax deductions.
Do Whatever You Can To Defray Costs.
Steve